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>

drizzle/meta/_journal.json

@@ -5,8 +5,8 @@
     {
       "idx": 0,
       "version": "6",
-      "when": 1769219562573,
-      "tag": "0000_busy_earthquake",
+      "when": 1769235451953,
+      "tag": "0000_flat_captain_marvel",
       "breakpoints": true
     }
   ]