chore: Remove old authentication configs and clean up environment files

Removed old/unused configuration files:
- .env (root) - Old Google OAuth production credentials (not used)
- .env.example (root) - Old Google OAuth template (replaced by Auth0)
- docker-compose.dev.yml - Old Keycloak setup (replaced by Auth0)
- Makefile - Unused build automation

Improved environment configuration:
- Created frontend/.env.example - Auth0 template for frontend
- Updated backend/.env.example:
  - Fixed port numbers (5433 for postgres, 6380 for redis)
  - Added clearer Auth0 setup instructions
  - Matches docker-compose.yml port configuration

Current setup:
- docker-compose.yml - PostgreSQL & Redis services (in use)
- backend/.env - Auth0 credentials (in use, not committed)
- frontend/.env - Auth0 credentials (in use, not committed)
- *.env.example files - Templates for new developers

All old Google OAuth and Keycloak references removed.
Application now runs on Auth0 only.

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

.claude/settings.local.json

@@ -35,7 +35,8 @@
       "Bash(dir:*)",
       "Bash(lsof:*)",
       "Bash(powershell -Command:*)",
-      "Bash(git rm:*)"
+      "Bash(git rm:*)",
+      "Bash(docker ps:*)"
     ]
   }
 }