fix(contacts): verify UID removal after CardDAV DELETE (#4642)

Add a post-delete verification step: after the CardDAV server returns
2xx/404, force-re-fetch the contact list and confirm the UID is gone.
If the UID is still present, log a warning and return False instead of
silently reporting success.

This catches the case where _resolve_resource_url falls back to the
guessed {uid}.vcf URL but the contact's real resource URL differs —
the DELETE hits the wrong URL, server returns 404 (treated as success),
but the contact remains. Previously this caused silent persistence
failures and agent loops.

routes/contacts_routes.py

@@ -689,15 +689,24 @@ def _delete_contact(uid: str) -> bool:
         url = _resolve_resource_url(uid)
         auth = (cfg["username"], cfg["password"]) if cfg["username"] else None
         r = httpx.delete(url, auth=auth, timeout=10)
-        if r.status_code in (200, 204):
-            _contact_cache["fetched_at"] = None
-            return True
-        if r.status_code == 404:
-            # Resource not found at the resolved URL. With href resolution
-            # this should be rare (genuinely already deleted). Invalidate
-            # the cache and report success so the UI doesn't keep a ghost.
-            logger.info(f"CardDAV DELETE 404 for {uid} — treating as already gone")
+        if r.status_code in (200, 204, 404):
+            # Invalidate cache so the next fetch sees the server truth.
             _contact_cache["fetched_at"] = None
+            # Verify: force a fresh fetch and check the UID is actually gone.
+            # A 404 on the guessed URL ({uid}.vcf) can mean the contact
+            # lives at a different resource URL — the DELETE missed it but
+            # we'd silently report success. This check catches that.
+            fresh = _fetch_contacts(force=True)
+            still_there = any(c.get("uid") == uid for c in fresh)
+            if still_there:
+                logger.warning(
+                    f"CardDAV DELETE reported success for {uid} "
+                    f"but UID still present after re-fetch — "
+                    f"resource URL may differ from {url}"
+                )
+                return False
+            if r.status_code == 404:
+                logger.info(f"CardDAV DELETE 404 for {uid} — already gone")
             return True
         logger.warning(f"CardDAV DELETE returned {r.status_code}: {r.text[:200]}")
         return False