feat: API key settings page — store ANTHROPIC/VOYAGE keys in DB with admin UI

- Migration: app_settings table with admin-only RLS (ANTHROPIC_API_KEY, VOYAGE_API_KEY)
- lib/settings.ts: getApiKey() reads DB first, falls back to env var
- lib/claude/client.ts: factory createAnthropicClient(apiKey) replaces singleton
- lib/claude/embed.ts: optional apiKey param, falls back to env
- 3 Claude AI routes + similar route: fetch key from settings before calling AI
- incidents/route.ts: fire-and-forget embed reads VOYAGE key from settings
- GET/POST /api/settings: admin-only masked key management endpoint
- /hse/settings page + ApiKeyForm client component

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FFDuBhMKvoWjrWT3ZnGmmr

lib/claude/embed.ts

@@ -1,10 +1,11 @@
-export async function embedText(text: string): Promise<number[]> {
-  if (!process.env.VOYAGE_API_KEY) throw new Error('VOYAGE_API_KEY is not set')
+export async function embedText(text: string, apiKey?: string): Promise<number[]> {
+  const key = apiKey ?? process.env.VOYAGE_API_KEY
+  if (!key) throw new Error('VOYAGE_API_KEY is not set')
   const res = await fetch('https://api.voyageai.com/v1/embeddings', {
     method: 'POST',
     headers: {
       'Content-Type': 'application/json',
-      'Authorization': `Bearer ${process.env.VOYAGE_API_KEY}`,
+      'Authorization': `Bearer ${key}`,
     },
     body: JSON.stringify({ input: [text], model: 'voyage-3-lite' }),
   })