Task #31: Let people leave, mute, or archive a group chat

Adds per-user mute / archive / leave actions for chats.

Schema:
- `lib/db/src/schema/conversations.ts`: added `is_muted` and
  `is_archived` boolean columns on `conversation_participants`.
- Columns applied directly via SQL (drizzle push wanted to make
  unrelated app_opens decisions; force-applied is_muted/is_archived
  with `ALTER TABLE ... ADD COLUMN IF NOT EXISTS`).

API (`artifacts/api-server/src/routes/conversations.ts`):
- New endpoint `PATCH /conversations/:id/state` — current user
  toggles their own `isMuted` / `isArchived`.
- New endpoint `POST /conversations/:id/leave` — removes the
  caller from a group conversation; rejects DMs.
- `buildConversationDetails` now returns `isMuted` and
  `isArchived` for the requesting user.
- `sendMessage` auto-clears `isArchived` for all participants so
  archived chats reappear when a new message arrives.

OpenAPI (`lib/api-spec/openapi.yaml`):
- Added the two new operations and `UpdateConversationStateBody`.
- Added `isMuted` / `isArchived` to `ConversationWithDetails`.
- Re-ran codegen for `@workspace/api-zod` and
  `@workspace/api-client-react`.

UI (`artifacts/teaboy-os/src/pages/chat.tsx`):
- Header gets a kebab "chat actions" button visible for both DMs
  and groups when a conversation is open.
- Action sheet offers Mute/Unmute, Archive/Unarchive, and
  (groups only) Leave with a confirmation dialog.
- Conversation list now has Active / Archived tabs and a
  bell-off indicator + dimmed unread badge for muted chats.
- Bilingual strings added to en.json and ar.json.

Side fixes (unrelated pre-existing schema drift discovered while
testing): added missing `users.clock_hour12` and
`conversations.avatar_url` columns directly so login and the
conversations list work; the schema files already declared them.

Verified end-to-end with the testing tool: mute, archive,
unarchive, and leave-group flows all pass.

lib/api-spec/openapi.yaml

@@ -729,6 +729,50 @@ paths:
               schema:
                 $ref: "#/components/schemas/ConversationWithDetails"
 
+  /conversations/{id}/state:
+    patch:
+      operationId: updateConversationState
+      tags: [conversations]
+      summary: Update per-user state (mute, archive)
+      parameters:
+        - name: id
+          in: path
+          required: true
+          schema:
+            type: integer
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: "#/components/schemas/UpdateConversationStateBody"
+      responses:
+        "200":
+          description: Updated conversation
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/ConversationWithDetails"
+
+  /conversations/{id}/leave:
+    post:
+      operationId: leaveConversation
+      tags: [conversations]
+      summary: Leave a group conversation
+      parameters:
+        - name: id
+          in: path
+          required: true
+          schema:
+            type: integer
+      responses:
+        "200":
+          description: Left conversation
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/SuccessResponse"
+
   /conversations/{id}/messages:
     get:
       operationId: listMessages
@@ -1458,6 +1502,10 @@ components:
           nullable: true
         unreadCount:
           type: integer
+        isMuted:
+          type: boolean
+        isArchived:
+          type: boolean
         createdAt:
           type: string
           format: date-time
@@ -1470,6 +1518,8 @@ components:
         - createdBy
         - participants
         - unreadCount
+        - isMuted
+        - isArchived
         - createdAt
         - updatedAt
 
@@ -1521,6 +1571,14 @@ components:
         nameEn:
           type: ["string", "null"]
 
+    UpdateConversationStateBody:
+      type: object
+      properties:
+        isMuted:
+          type: boolean
+        isArchived:
+          type: boolean
+
     AddParticipantsBody:
       type: object
       properties: