feat: admin panel with SQLite, auth, and calendar-style schedule editor

Complete admin panel for content management:
- SQLite database with better-sqlite3, seed script from content.ts
- Simple password auth with HMAC-signed cookies (Edge + Node compatible)
- 9 section editors: meta, hero, about, team, classes, schedule, pricing, FAQ, contact
- Team CRUD with image upload and drag reorder
- Schedule editor with Google Calendar-style visual timeline (colored blocks, overlap detection, click-to-add)
- All public components refactored to accept data props from DB (with fallback to static content)
- Middleware protecting /admin/* and /api/admin/* routes

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

package.json

@@ -6,9 +6,11 @@
     "dev": "next dev",
     "build": "next build",
     "start": "next start",
-    "lint": "next lint"
+    "lint": "next lint",
+    "seed": "tsx src/data/seed.ts"
   },
   "dependencies": {
+    "better-sqlite3": "^12.6.2",
     "lucide-react": "^0.576.0",
     "next": "16.1.6",
     "react": "19.2.3",
@@ -16,6 +18,7 @@
   },
   "devDependencies": {
     "@tailwindcss/postcss": "^4",
+    "@types/better-sqlite3": "^7.6.13",
     "@types/node": "^20",
     "@types/react": "^19",
     "@types/react-dom": "^19",
@@ -24,6 +27,7 @@
     "eslint-config-prettier": "^10.1.8",
     "prettier": "^3.8.1",
     "tailwindcss": "^4",
+    "tsx": "^4.21.0",
     "typescript": "^5"
   }
 }