Add edit and delete to task modal

Edit button (update cap): inline form for title, description, priority, unusable flag, due date. Delete button (admin only): hard delete with confirm step, cascades photos/events and cleans files from disk. Backend adds DELETE /api/tasks/:id route.

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

frontend/src/api.ts

@@ -75,6 +75,9 @@ export function createTask(body: Record<string, unknown>): Promise<Task> {
 export function updateTask(id: number, body: Record<string, unknown>): Promise<Task> {
   return request(`/tasks/${id}`, { method: 'PATCH', body: JSON.stringify(body) })
 }
+export function deleteTask(id: number): Promise<{ ok: boolean }> {
+  return request(`/tasks/${id}`, { method: 'DELETE' })
+}
 export function resolveTask(id: number, body: {
   status: 'temporary_fix' | 'fixed'
   completed_by?: string