feat(phase-4a): complete Phase 3 implementation and gap analysis

Merges Phase 4a work including:

Implementation:
- Metadata discovery endpoint (/api/.well-known/oauth-authorization-server)
- h-app microformat parser service
- Enhanced authorization endpoint with client info display
- Configuration management system
- Dependency injection framework

Documentation:
- Comprehensive gap analysis for v1.0.0 compliance
- Phase 4a clarifications on development approach
- Phase 4-5 critical components breakdown

Testing:
- Unit tests for h-app parser (308 lines, comprehensive coverage)
- Unit tests for metadata endpoint (134 lines)
- Unit tests for configuration system (18 lines)
- Integration test updates

All tests passing with high coverage. Ready for Phase 4b security hardening.

tests/integration/test_health.py

@@ -23,6 +23,7 @@ class TestHealthEndpoint:
 
             # Set required environment variables
             monkeypatch.setenv("GONDULF_SECRET_KEY", "a" * 32)
+            monkeypatch.setenv("GONDULF_BASE_URL", "https://auth.example.com")
             monkeypatch.setenv("GONDULF_DATABASE_URL", f"sqlite:///{db_path}")
             monkeypatch.setenv("GONDULF_DEBUG", "true")
 
@@ -79,6 +80,7 @@ class TestHealthCheckUnhealthy:
         """Test health check returns 503 when database inaccessible."""
         # Set up with non-existent database path
         monkeypatch.setenv("GONDULF_SECRET_KEY", "a" * 32)
+        monkeypatch.setenv("GONDULF_BASE_URL", "https://auth.example.com")
         monkeypatch.setenv(
             "GONDULF_DATABASE_URL", "sqlite:////nonexistent/path/db.db"
         )