Add user authentication with login/register

- Add users and sessions tables to database schema
- Add bcryptjs for password hashing
- Create auth API routes (login, register, logout, me)
- Add AuthProvider context for client-side auth state
- Update all API routes to require authentication and filter by userId
- Create login and register pages
- Add AppShell component for authenticated layout
- Update all pages to use AppShell and show user info
- Each user now has their own private entries and tags

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

package.json

@@ -12,6 +12,7 @@
     "db:studio": "drizzle-kit studio"
   },
   "dependencies": {
+    "bcryptjs": "^3.0.3",
     "better-sqlite3": "^12.6.2",
     "drizzle-orm": "^0.45.1",
     "lucide-react": "^0.562.0",
@@ -22,6 +23,7 @@
   },
   "devDependencies": {
     "@tailwindcss/postcss": "^4",
+    "@types/bcryptjs": "^2.4.6",
     "@types/better-sqlite3": "^7.6.13",
     "@types/node": "^20",
     "@types/react": "^19",