Server and infrastructure updates:
- Initialize auth middleware with JWT validation
- Remove OAuth route registration
- Update imports to use new auth package
- Clean up unused OAuth configuration
- Update PDS provisioning comments for clarity
- Fix repository query parameter ordering

These changes complete the migration from OAuth to JWT-based auth
throughout the application initialization and routing layers.

Update integration tests to pass access tokens:
- Pass accessToken to SubscribeToCommunity() calls
- Add comments explaining token usage in tests
- Verify subscribe/unsubscribe E2E flows with real auth

Tests now validate the complete authentication chain:
1. User authenticates with PDS (gets access token)
2. User makes request with Authorization header
3. Middleware validates JWT and stores token
4. Handler extracts token from context
5. Service uses token to write to user's PDS repo
6. PDS validates user owns the repository
7. Record successfully written

All E2E tests pass with real PDS authentication.

Update community handlers to pass user tokens through:

Subscribe/Unsubscribe handlers:
- Extract user access token from request context
- Validate token presence (return 401 if missing)
- Pass token to service layer for PDS operations

Create/Update handlers:
- Update comments to clarify security model
- Document that createdByDid/updatedByDid come from JWT
- Document that hostedByDid is server-side derived

This completes the token flow: middleware → handlers → service → PDS,
ensuring each layer has the credentials needed for proper authorization.

Update subscription methods to accept and use user access tokens:
- Add userAccessToken parameter to SubscribeToCommunity()
- Add userAccessToken parameter to UnsubscribeFromCommunity()
- Add deleteRecordOnPDSAs() helper for user-scoped deletions
- Use createRecordOnPDSAs() for subscription creation
- Validate token presence before PDS operations

This fixes the authorization issue where we were using instance
credentials to write to user repositories, which the PDS correctly
rejected with 401 errors.

Now each user operation uses that user's own access token, ensuring
proper atProto authorization semantics.

Extend auth middleware to preserve user access tokens:
- Add UserAccessToken context key
- Store tokens in both RequireAuth and OptionalAuth flows
- Add GetUserAccessToken() helper function
- Add comprehensive test coverage for token extraction

This enables downstream handlers and services to use the user's
actual access token when performing operations on their behalf,
ensuring proper authorization when writing to user PDS repositories.

Critical for user-scoped operations like subscribe/unsubscribe where
we must authenticate as the user, not the instance.

Add new simplified authentication system:
- JWT parsing and validation against atProto standards
- JWKS fetcher with caching for PDS public keys
- Support for both signature verification and parse-only modes
- Claims extraction (sub, iss, aud, exp, iat)

Dependencies:
- Add github.com/golang-jwt/jwt/v5 for JWT handling

This replaces the complex OAuth/DPoP flow with direct JWT validation,
suitable for alpha phase where we control both the PDS and AppView.

Files:
- internal/atproto/auth/jwt.go: JWT parsing and verification
- internal/atproto/auth/jwks_fetcher.go: Public key fetching
- internal/atproto/auth/jwt_test.go: Test coverage
- internal/atproto/auth/README.md: Documentation