Refactor authentication and session management

- Removed session-based user retrieval from dependencies.py and main.py.
- Eliminated SessionMiddleware and related session handling code.
- Updated dashboard and team views to directly query user data from the database.
- Simplified redeem and team management views to remove authentication checks.
- Adjusted templates to reflect changes in user context handling.
- Added camera selection feature in scan_qr.html for improved QR code scanning.
- Cleaned up Docker configuration and requirements for better deployment.

requirements.txt

@@ -25,4 +25,7 @@ aiofiles>=23.2.1
 python-dotenv>=1.0.0
 email-validator>=2.0.0
 pydantic>=2.3.0
-qrcode>=7.4.2
+qrcode>=7.4.2
+
+# Image processing library for QR code generation
+Pillow>=9.0.0