feat(psa): implement post_note and update_ticket_status in CW provider

Replaces NotImplementedError stubs with working implementations:
- post_note maps note_type to CW flag fields (internalAnalysisFlag,
  resolutionFlag, detailDescriptionFlag) with appropriate visibility
  and notification settings
- update_ticket_status uses CW JSON Patch format to update status

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/services/psa/connectwise/provider.py

@@ -155,7 +155,7 @@ class ConnectWiseProvider(PSAProvider):
             status=data.get("status", {}).get("name") if data.get("status") else None,
         )
 
-    # ── Stubs for later slices ────────────────────────────────────────
+    # ── Notes & status updates ───────────────────────────────────────
 
     async def post_note(
         self,
@@ -164,12 +164,71 @@ class ConnectWiseProvider(PSAProvider):
         note_type: str,
         member_id: str | None = None,
     ) -> PSANote:
-        raise NotImplementedError("Implemented in Slice 4")
+        """Post a note to a CW ticket.
+
+        Maps ResolutionFlow note types to CW flag fields:
+        - internal_analysis → internalAnalysisFlag (internal only)
+        - resolution → resolutionFlag (internal, triggers notifications)
+        - description → detailDescriptionFlag (external, triggers notifications)
+        """
+        from app.services.psa.types import NoteType
+
+        flags = {
+            NoteType.INTERNAL_ANALYSIS: {
+                "internalAnalysisFlag": True,
+                "resolutionFlag": False,
+                "detailDescriptionFlag": False,
+                "internalFlag": True,
+                "processNotifications": False,
+            },
+            NoteType.RESOLUTION: {
+                "internalAnalysisFlag": False,
+                "resolutionFlag": True,
+                "detailDescriptionFlag": False,
+                "internalFlag": True,
+                "processNotifications": True,
+            },
+            NoteType.DESCRIPTION: {
+                "internalAnalysisFlag": False,
+                "resolutionFlag": False,
+                "detailDescriptionFlag": True,
+                "internalFlag": False,
+                "processNotifications": True,
+            },
+        }
+
+        note_flags = flags.get(note_type, flags[NoteType.INTERNAL_ANALYSIS])
+
+        body: dict = {
+            "text": text,
+            **note_flags,
+        }
+
+        if member_id:
+            body["member"] = {"id": int(member_id)}
+
+        data = await self.client.post(
+            f"/service/tickets/{ticket_id}/notes", json_body=body
+        )
+
+        return PSANote(
+            id=str(data.get("id", "")),
+            text=data.get("text", ""),
+            note_type=note_type,
+            created_at=data.get("dateCreated"),
+        )
 
     async def update_ticket_status(
         self, ticket_id: str, status_id: int
     ) -> PSATicket:
-        raise NotImplementedError("Implemented in Slice 4")
+        """Update a CW ticket's status using JSON Patch format."""
+        patch_body = [
+            {"op": "replace", "path": "status", "value": {"id": status_id}}
+        ]
+        data = await self.client.patch(
+            f"/service/tickets/{ticket_id}", json_body=patch_body
+        )
+        return self._map_ticket(data)
 
     async def list_members(self) -> list[PSAMember]:
         raise NotImplementedError("Implemented in Slice 5")