Add database setup script and fix dark mode visibility

- Add scripts/setup-db.ts to programmatically create missing PocketBase
  collections (period_logs, dailyLogs) with proper relation fields
- Fix dark mode visibility across settings, login, calendar, and dashboard
  components by using semantic CSS tokens and dark: variants
- Add db:setup npm script and document usage in AGENTS.md
- Update vitest config to include scripts directory tests

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

package.json

@@ -9,7 +9,8 @@
     "lint": "biome check .",
     "lint:fix": "biome check --write .",
     "test": "vitest",
-    "test:run": "vitest run"
+    "test:run": "vitest run",
+    "db:setup": "npx tsx scripts/setup-db.ts"
   },
   "dependencies": {
     "class-variance-authority": "^0.7.1",