Add settings page for managing forecasting API key and URL via UI

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/node_modules/@reduxjs/toolkit/skills/model-redux-state/design-state-ownership/SKILL.md

@@ -0,0 +1,322 @@
+---
+name: model-redux-state/design-state-ownership
+description: >
+  Use this when deciding whether data belongs in Redux, component state, router
+  state, or another external source. Covers state ownership, authority
+  boundaries, slice sizing, and when to move or split data as the app evolves.
+type: core
+library: "@reduxjs/toolkit"
+library_version: "2.11.2"
+sources:
+  - "reduxjs/redux:docs/style-guide/style-guide.md"
+  - "reduxjs/redux:docs/tutorials/essentials/part-2-app-structure.md"
+  - "reduxjs/redux:docs/tutorials/essentials/part-4-using-data.md"
+---
+
+# Design State Ownership
+
+## Setup
+
+```tsx
+import { useState } from 'react'
+import { createSlice } from '@reduxjs/toolkit'
+import { useAppDispatch } from '../../app/hooks'
+
+const postsSlice = createSlice({
+  name: 'posts',
+  initialState: [] as { id: string; title: string; content: string }[],
+  reducers: {
+    postAdded(
+      state,
+      action: { payload: { id: string; title: string; content: string } },
+    ) {
+      state.push(action.payload)
+    },
+  },
+})
+
+const { postAdded } = postsSlice.actions
+
+export function AddPostForm() {
+  const [title, setTitle] = useState('')
+  const [content, setContent] = useState('')
+  const dispatch = useAppDispatch()
+
+  return (
+    <form
+      onSubmit={(event) => {
+        event.preventDefault()
+        dispatch(postAdded({ id: 'p1', title, content }))
+      }}
+    >
+      <input value={title} onChange={(event) => setTitle(event.target.value)} />
+      <textarea
+        value={content}
+        onChange={(event) => setContent(event.target.value)}
+      />
+      <button type="submit">Save</button>
+    </form>
+  )
+}
+```
+
+## Core Patterns
+
+### Keep editable form state local until the user commits it
+
+```tsx
+import { useState } from 'react'
+import { useAppDispatch } from '../../app/hooks'
+import { profileSaved } from './profileSlice'
+
+export function ProfileForm() {
+  const [displayName, setDisplayName] = useState('Lenz')
+  const dispatch = useAppDispatch()
+
+  return (
+    <form
+      onSubmit={(event) => {
+        event.preventDefault()
+        dispatch(profileSaved({ displayName }))
+      }}
+    >
+      <input
+        value={displayName}
+        onChange={(event) => setDisplayName(event.target.value)}
+      />
+      <button type="submit">Save</button>
+    </form>
+  )
+}
+```
+
+Prefer Redux for shared, durable app state, not every keystroke.
+
+### Keep URL state with the router and combine it at the edge
+
+```tsx
+import { createSelector } from '@reduxjs/toolkit'
+import { useSearchParams } from 'react-router-dom'
+import { useAppSelector } from '../../app/hooks'
+
+type RootState = {
+  posts: {
+    items: { id: string; title: string; published: boolean }[]
+  }
+}
+
+const selectPosts = (state: RootState) => state.posts.items
+
+const selectVisiblePosts = createSelector(
+  [selectPosts, (_state: RootState, filter: string) => filter],
+  (posts, filter) =>
+    filter === 'published'
+      ? posts.filter((post) => post.published)
+      : posts,
+)
+
+export function PostsList() {
+  const [searchParams] = useSearchParams()
+  const filter = searchParams.get('filter') ?? 'all'
+  const posts = useAppSelector((state) => selectVisiblePosts(state, filter))
+
+  return <div>{posts.length}</div>
+}
+```
+
+If the router already owns a piece of state, pass it into selectors or combine it in the component instead of syncing it into Redux.
+
+### Re-size slices when access patterns change
+
+```ts
+import { combineReducers, createSlice } from '@reduxjs/toolkit'
+
+const authSlice = createSlice({
+  name: 'auth',
+  initialState: { userId: null as string | null },
+  reducers: {},
+})
+
+const postsSlice = createSlice({
+  name: 'posts',
+  initialState: { items: [] as { id: string; title: string }[] },
+  reducers: {},
+})
+
+export const rootReducer = combineReducers({
+  auth: authSlice.reducer,
+  posts: postsSlice.reducer,
+})
+```
+
+Revisit slice size over time; unrelated data should split apart, and data constantly stitched together in every component may belong closer together.
+
+## Common Mistakes
+
+### MEDIUM Putting form editing state in Redux
+
+Wrong:
+
+```tsx
+import { useAppSelector } from '../../app/hooks'
+
+const selectDraftTitle = (state: { draft: { title: string } }) => state.draft.title
+
+const title = useAppSelector(selectDraftTitle)
+```
+
+Correct:
+
+```tsx
+const [title, setTitle] = useState('')
+
+<input value={title} onChange={(event) => setTitle(event.target.value)} />
+```
+
+Per-keystroke dispatching adds global complexity for data that usually lives in one component tree.
+
+Source: reduxjs/redux:docs/style-guide/style-guide.md
+
+### HIGH Synchronizing router or URL state into Redux
+
+Wrong:
+
+```tsx
+import { useEffect } from 'react'
+import { useSearchParams } from 'react-router-dom'
+import { useAppDispatch } from '../../app/hooks'
+
+function PostsPage() {
+  const [searchParams] = useSearchParams()
+  const dispatch = useAppDispatch()
+
+useEffect(() => {
+  dispatch(filterChanged(searchParams.get('filter') ?? 'all'))
+}, [dispatch, searchParams])
+
+  return null
+}
+```
+
+Correct:
+
+```tsx
+const filter = searchParams.get('filter') ?? 'all'
+const posts = useAppSelector((state) => selectVisiblePosts(state, filter))
+```
+
+URL state already has an authoritative owner; duplicating it into Redux creates two sources of truth.
+
+Source: maintainer interview
+
+### HIGH Naming state after components
+
+Wrong:
+
+```ts
+import { combineReducers } from '@reduxjs/toolkit'
+
+const loginReducer = (state = { open: false }) => state
+const postsReducer = (state = [] as { id: string; title: string }[]) => state
+
+const rootReducer = combineReducers({
+  loginScreen: loginReducer,
+  postsList: postsReducer,
+})
+```
+
+Correct:
+
+```ts
+import { combineReducers } from '@reduxjs/toolkit'
+
+const authReducer = (state = { userId: null as string | null }) => state
+const postsReducer = (state = [] as { id: string; title: string }[]) => state
+
+const rootReducer = combineReducers({
+  auth: authReducer,
+  posts: postsReducer,
+})
+```
+
+Store keys should describe data or domain concepts, not the current component tree.
+
+Source: reduxjs/redux:docs/style-guide/style-guide.md
+
+### MEDIUM Letting slice boundaries fossilize
+
+Wrong:
+
+```ts
+import { createSlice } from '@reduxjs/toolkit'
+
+type Post = { id: string; title: string }
+type AppNotification = { id: string; message: string }
+
+const appSlice = createSlice({
+  name: 'app',
+  initialState: {
+    auth: { userId: null as string | null },
+    posts: [] as Post[],
+    notifications: [] as AppNotification[],
+  },
+  reducers: {},
+})
+```
+
+Correct:
+
+```ts
+import { createSlice } from '@reduxjs/toolkit'
+
+type Post = { id: string; title: string }
+
+const authSlice = createSlice({
+  name: 'auth',
+  initialState: { userId: null as string | null },
+  reducers: {},
+})
+
+const postsSlice = createSlice({
+  name: 'posts',
+  initialState: [] as Post[],
+  reducers: {},
+})
+```
+
+When unrelated data is welded together, every change point gets noisier; split or merge slices as actual access patterns demand.
+
+Source: maintainer interview
+
+### HIGH Blindly spreading payloads into state
+
+Wrong:
+
+```ts
+const state = { id: '1', name: 'Lenz' }
+const action = { payload: { id: '2', name: 'Mark', ignored: true } }
+
+userLoggedIn(state, action) {
+  return { ...state, ...action.payload }
+}
+```
+
+Correct:
+
+```ts
+const state = { id: '1', name: 'Lenz' }
+const action = { payload: { id: '2', name: 'Mark', ignored: true } }
+
+userLoggedIn(state, action) {
+  state.id = action.payload.id
+  state.name = action.payload.name
+}
+```
+
+Reducers should own the slice shape instead of treating payloads as trusted state patches.
+
+Source: reduxjs/redux:docs/style-guide/style-guide.md
+
+## References
+
+- [State ownership heuristics](references/state-ownership.md)

frontend/node_modules/@reduxjs/toolkit/skills/model-redux-state/design-state-ownership/references/state-ownership.md

@@ -0,0 +1,28 @@
+# State Ownership Heuristics
+
+## Choose the owner, then the tool
+
+| Kind of state | Default owner | Typical tool |
+| --- | --- | --- |
+| Editable form fields | Component | `useState` |
+| Shared mutable app data | Redux | Slice state |
+| Server cache | RTK Query | `createApi` |
+| URL, pathname, search params | Router | Router APIs plus selector inputs |
+| Browser-only authority like `localStorage` | External source | Read at boundaries, then dispatch events |
+
+## Good reasons to move data into Redux
+
+- Multiple distant parts of the UI need the same mutable data.
+- You need time-travel debugging or a stable action history.
+- The reducer should own transitions because they mix old store state with new inputs.
+
+## Reasons to keep data out of Redux
+
+- Another system already owns it, such as the router.
+- It only matters during editing inside one component tree.
+- It is server cache and RTK Query fits the use case better.
+
+## Re-evaluate slice size
+
+- If data is constantly stitched together outside reducers, it may belong closer together.
+- If unrelated updates keep touching the same slice, split the slice by domain ownership.