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/es-toolkit/dist/string/startCase.d.ts

@@ -0,0 +1,17 @@
+//#region src/string/startCase.d.ts
+/**
+ * Converts the first character of each word in a string to uppercase and the remaining characters to lowercase.
+ *
+ * Start case is the naming convention in which each word is written with an initial capital letter.
+ * @param str - The string to convert.
+ * @returns The converted string.
+ *
+ * @example
+ * const result1 = startCase('hello world');  // result will be 'Hello World'
+ * const result2 = startCase('HELLO WORLD');  // result will be 'Hello World'
+ * const result3 = startCase('hello-world');  // result will be 'Hello World'
+ * const result4 = startCase('hello_world');  // result will be 'Hello World'
+ */
+declare function startCase(str: string): string;
+//#endregion
+export { startCase };