feat: ConnectWise PSA integration (#106)

PSA abstraction layer with provider pattern, ConnectWise integration (connection management, ticket linking, note posting, status updates, member mapping), Integrations page UI, Fernet credential encryption, in-memory TTL cache, 6 DB migrations, ConnectWise API reference docs.

backend/app/core/config.py

@@ -119,6 +119,16 @@ class Settings(BaseSettings):
         """Check if any AI provider is configured."""
         return self.ANTHROPIC_API_KEY is not None or self.GOOGLE_AI_API_KEY is not None
 
+    # ConnectWise PSA Integration
+    # CW_CLIENT_ID is a product-level GUID registered at developer.connectwise.com
+    # All MSP customers share this single clientId — it identifies ResolutionFlow as the integration
+    CW_CLIENT_ID: Optional[str] = None
+
+    @property
+    def cw_enabled(self) -> bool:
+        """Check if ConnectWise integration is configured."""
+        return self.CW_CLIENT_ID is not None
+
     # Monitoring
     SENTRY_DSN: Optional[str] = None