Fix CI/CD issues and add comprehensive tests for multi-user features

This commit fixes three critical issues identified in CI/CD and adds
comprehensive test coverage for the new multi-user functionality.

## Fixes

### 1. FastMCP Middleware Registration Error

**Problem**: `AttributeError: 'FastMCP' object has no attribute 'app'`

**Solution**: Implemented robust middleware registration that:
- Tries multiple possible locations where FastMCP might store the app
- Gracefully handles cases where app isn't immediately available
- Wraps the run() method to defer middleware addition if needed
- Attempts: _transport.app, sse.app, http_server.app, _app, _asgi_app
- Falls back gracefully with warning if middleware can't be added

**Files Changed**:
- src/geoguessr_mcp/main.py: Added smart middleware registration logic

### 2. Test Permission Errors

**Problem**: `PermissionError: [Errno 13] Permission denied: '/app'`
Schema registry tried to create /app/data/schemas in CI without permission

**Solution**: Made schema cache directory creation fault-tolerant:
- Catches PermissionError and OSError when creating cache directory
- Falls back to temporary directory (tempfile.mkdtemp) if permission denied
- Logs clear warning messages about fallback behavior
- Tests can now run in restricted environments

**Files Changed**:
- src/geoguessr_mcp/monitoring/schema/schema_registry.py: Added fallback logic

### 3. Black Formatting Issues

**Problem**: 10 files needed reformatting

**Solution**: Ran `black src/ --line-length 100` on all source files

**Files Formatted**:
- src/geoguessr_mcp/config.py
- src/geoguessr_mcp/api/dynamic_response.py
- src/geoguessr_mcp/middleware/auth.py
- src/geoguessr_mcp/main.py
- src/geoguessr_mcp/auth/multi_user_session.py
- src/geoguessr_mcp/tools/auth_tools.py
- src/tests/integration/test_auth_flow.py
- src/tests/unit/services/*.py (3 files)

## New Tests

Added comprehensive test coverage for multi-user features:

### test_user_context.py
- Tests UserContext creation with/without sessions
- Tests authentication status checking
- Tests session expiration handling
- Tests string representation
- Tests API key hashing for anonymous users
- Tests consistency of anonymous user IDs

### test_multi_user_session.py
- Tests MultiUserSessionManager initialization
- Tests session manager creation per API key
- Tests session manager reuse for same API key
- Tests isolation between different users
- Tests auth status reporting
- Tests context creation and retrieval

### test_request_context.py
- Tests context variable get/set operations
- Tests require_user_context() error handling
- Tests context isolation between requests
- Tests context updates and clearing
- Tests None handling

## Code Quality

All changes pass:
- ✅ Python syntax checks (py_compile)
- ✅ Black formatting (line-length 100)
- ✅ Test structure validation
- ✅ Import resolution

## CI/CD Impact

These fixes should resolve:
- ❌ Test execution failures (permission errors)
- ❌ Black formatting check failures
- ❌ Runtime errors when starting server with auth enabled

Tests can now run in CI environment without requiring:
- Root permissions
- /app directory access
- Pre-created cache directories

src/tests/unit/auth/test_user_context.py

@@ -0,0 +1,95 @@
+"""Tests for UserContext class."""
+
+import pytest
+
+from geoguessr_mcp.auth.session import UserSession
+from geoguessr_mcp.auth.user_context import UserContext
+from datetime import datetime, timedelta, UTC
+
+
+class TestUserContext:
+    """Tests for UserContext class."""
+
+    def test_user_context_without_session(self):
+        """Test user context without a GeoGuessr session."""
+        context = UserContext(api_key="test_key_123")
+
+        assert context.api_key == "test_key_123"
+        assert context.session is None
+        assert not context.is_authenticated
+        assert context.ncfa_cookie is None
+        assert "anonymous_" in context.user_id
+        assert "User-" in context.username
+
+    def test_user_context_with_session(self):
+        """Test user context with a GeoGuessr session."""
+        session = UserSession(
+            ncfa_cookie="test_cookie",
+            user_id="user123",
+            username="testuser",
+            email="test@example.com",
+            expires_at=datetime.now(UTC) + timedelta(days=1),
+        )
+
+        context = UserContext(api_key="test_key_123", session=session)
+
+        assert context.api_key == "test_key_123"
+        assert context.session == session
+        assert context.is_authenticated
+        assert context.ncfa_cookie == "test_cookie"
+        assert context.user_id == "user123"
+        assert context.username == "testuser"
+
+    def test_user_context_with_expired_session(self):
+        """Test user context with an expired session."""
+        session = UserSession(
+            ncfa_cookie="test_cookie",
+            user_id="user123",
+            username="testuser",
+            email="test@example.com",
+            expires_at=datetime.now(UTC) - timedelta(days=1),  # Expired
+        )
+
+        context = UserContext(api_key="test_key_123", session=session)
+
+        # Session is present but not valid
+        assert context.session == session
+        assert not context.is_authenticated  # Expired session = not authenticated
+
+    def test_user_context_repr(self):
+        """Test string representation of user context."""
+        context = UserContext(api_key="test_key_123")
+        repr_str = repr(context)
+
+        assert "UserContext" in repr_str
+        assert "not authenticated" in repr_str
+
+        session = UserSession(
+            ncfa_cookie="test_cookie",
+            user_id="user123",
+            username="testuser",
+            email="test@example.com",
+        )
+        context_with_session = UserContext(api_key="test_key_123", session=session)
+        repr_with_session = repr(context_with_session)
+
+        assert "authenticated" in repr_with_session
+        assert "user123" in repr_with_session
+
+    def test_user_context_consistent_ids(self):
+        """Test that user IDs are consistent for the same API key."""
+        context1 = UserContext(api_key="same_key")
+        context2 = UserContext(api_key="same_key")
+
+        # Same API key should produce same anonymous user ID
+        assert context1.user_id == context2.user_id
+        assert context1.username == context2.username
+
+    def test_user_context_different_ids_for_different_keys(self):
+        """Test that different API keys produce different anonymous user IDs."""
+        context1 = UserContext(api_key="key1")
+        context2 = UserContext(api_key="key2")
+
+        # Different API keys should produce different anonymous user IDs
+        assert context1.user_id != context2.user_id
+        assert context1.username != context2.username