test(contacts): cover blocked relation for add-by-email

docs/api-reference.md

@@ -666,6 +666,11 @@ Body:
 
 Response: `204`
 
+Errors:
+
+- `404` - user with this email was not found.
+- `409` - contact cannot be added because a block relation exists.
+
 ### DELETE `/api/v1/users/{user_id}/contacts`
 
 Auth required.  

docs/core-checklist-status.md

@@ -10,7 +10,7 @@ Legend:
 1. Account - `PARTIAL` (email auth, JWT, refresh, logout, reset; sessions exist, full UX still improving)
 2. User Profile - `DONE` (username, name, avatar, bio, update)
 3. User Status - `PARTIAL` (online/last seen/offline; "recently" heuristic limited)
-4. Contacts - `PARTIAL` (list/search/add/remove/block/unblock; `add by email` flow covered by integration tests; UX moved to menu)
+4. Contacts - `PARTIAL` (list/search/add/remove/block/unblock; `add by email` flow covered by integration tests including `success/not found/blocked conflict`; UX moved to menu)
 5. Chat List - `DONE` (all/pinned/archive/sort/unread)
 6. Chat Types - `DONE` (private/group/channel)
 7. Chat Creation - `DONE` (private/group/channel)