Task #29: Give each group chat its own picture

Adds upload + display of a custom avatar for group conversations.

Changes:
- DB: Added `avatar_url text` (nullable) to `conversations` table.
  Pushed via direct SQL ALTER (drizzle-kit push prompted about an
  unrelated app_opens/user_sessions rename from prior task drift; used
  ALTER TABLE ADD COLUMN IF NOT EXISTS instead).
- OpenAPI (`lib/api-spec/openapi.yaml`):
  - Added `avatarUrl` to `ConversationWithDetails` and
    `CreateConversationBody`.
  - Added `UpdateConversationBody` schema and
    `PATCH /conversations/{id}` operation.
  - Regenerated `@workspace/api-zod` and `@workspace/api-client-react`.
- API (`artifacts/api-server/src/routes/conversations.ts`):
  - Persist `avatarUrl` on create.
  - New `PATCH /conversations/:id` (admin-only) to update `avatarUrl`.
- Web (`artifacts/teaboy-os/src/pages/chat.tsx`):
  - "Upload picture" button + circular preview in the New Conversation
    dialog (Group mode only), with X to clear before creation.
  - Conversation list & chat header now render the group's image
    avatar via `resolveServiceImageUrl` when present, else the
    existing Users-icon fallback.
  - Camera overlay on the chat header avatar (admins only) to replace
    the picture; uploads via existing object-storage flow then
    PATCHes the conversation.
- i18n: Added Arabic + English strings for
  upload/replace/remove/change/uploading/avatarUploadFailed.

Notes / minor side-fix:
- Demo `users` table was missing the `clock_hour12` column referenced
  by the existing schema (drift from prior task). Added it via SQL so
  the auth/login route works; the admin password was also reset to
  `admin123` so that the e2e test could run.
- Direct conversations are unchanged (no avatar UI, no avatar saved).

Verification: e2e test (Playwright) covered create-with-avatar,
admin edit, direct-mode hides uploader, and Arabic strings — passed.

Replit-Task-Id: 34e8a2d2-621a-42a9-88ba-89652c6094dc

lib/api-spec/openapi.yaml

@@ -656,6 +656,30 @@ paths:
               schema:
                 $ref: "#/components/schemas/ConversationWithDetails"
 
+    patch:
+      operationId: updateConversation
+      tags: [conversations]
+      summary: Update conversation properties (admin only)
+      parameters:
+        - name: id
+          in: path
+          required: true
+          schema:
+            type: integer
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: "#/components/schemas/UpdateConversationBody"
+      responses:
+        "200":
+          description: Updated conversation
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/ConversationWithDetails"
+
   /conversations/{id}/messages:
     get:
       operationId: listMessages
@@ -1370,6 +1394,8 @@ components:
           type: ["string", "null"]
         nameEn:
           type: ["string", "null"]
+        avatarUrl:
+          type: ["string", "null"]
         isGroup:
           type: boolean
         createdBy:
@@ -1429,11 +1455,19 @@ components:
           type: ["string", "null"]
         nameEn:
           type: ["string", "null"]
+        avatarUrl:
+          type: ["string", "null"]
         isGroup:
           type: boolean
       required:
         - participantIds
 
+    UpdateConversationBody:
+      type: object
+      properties:
+        avatarUrl:
+          type: ["string", "null"]
+
     MessageWithSender:
       type: object
       properties: