Task #28: Let users pick a 12-hour (AM/PM) clock instead of 24-hour

Add a per-user 12/24-hour clock preference that complements the existing
clock-style preference and is honored by every clock variant on the home
screen.

Schema & API
- Added `clockHour12 boolean` (nullable) column to `users` table
  (lib/db/src/schema/users.ts) and synced via direct `ALTER TABLE`
  because `drizzle-kit push` was blocked by an unrelated interactive
  rename prompt for the existing `app_opens` table.
- Extended OpenAPI `AuthUser` and `UserProfile` with `clockHour12`,
  added `UpdateClockHour12Body` schema, and a new
  `PATCH /auth/me/clock-hour12` endpoint. Regenerated zod + react-query
  clients via `pnpm --filter @workspace/api-spec run codegen`.
- Implemented the new route handler in
  `artifacts/api-server/src/routes/auth.ts`; `buildAuthUser` now
  surfaces `clockHour12`.

Frontend
- `lib/i18n-format.ts` no longer hard-codes `hour12: false`; callers
  may pass `hour12` in options. Default remains 24-hour to keep all
  other timestamps unchanged (chat etc. left as-is — see follow-up).
- `components/clock.tsx` exports `resolveClockHour12` and threads a new
  `hour12` prop through `Clock` and `AnalogClockWidget`. All five
  variants (full/digital/digital-no-seconds/analog/minimal) plus the
  large analog widget now honor the choice.
- `components/clock-style-picker.tsx` gained a 12-hour / 24-hour
  segmented toggle that calls the new endpoint with optimistic cache
  updates. The variant previews also reflect the active hour format.
- `pages/home.tsx` passes `user.clockHour12` to the header clock,
  widget, and picker.
- Added `home.clockStyle.hourFormat.{label,h12,h24}` strings in EN and
  AR. Arabic uses Latin digits and "ص/م" via Intl's localized
  dayPeriod.

Verification
- `pnpm -w run typecheck` passes.
- E2E test: logged in, switched to 12-hour, verified AM/PM in header
  and previews, reloaded to confirm persistence, switched back to
  24-hour, reloaded again — all green.

Replit-Task-Id: 03ea8cbe-ace7-4d36-afc5-49ebc9706c67

lib/api-spec/openapi.yaml

@@ -270,6 +270,31 @@ paths:
               schema:
                 $ref: "#/components/schemas/ErrorResponse"
 
+  /auth/me/clock-hour12:
+    patch:
+      operationId: updateClockHour12
+      tags: [auth]
+      summary: Update preferred 12/24-hour clock format
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: "#/components/schemas/UpdateClockHour12Body"
+      responses:
+        "200":
+          description: Updated
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/AuthUser"
+        "400":
+          description: Validation error
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/ErrorResponse"
+
   # Apps
   /apps:
     get:
@@ -1025,6 +1050,15 @@ components:
       required:
         - clockStyle
 
+    UpdateClockHour12Body:
+      type: object
+      properties:
+        clockHour12:
+          type: ["boolean", "null"]
+          description: Whether to use 12-hour (AM/PM) clock format; null clears and uses the default (24-hour)
+      required:
+        - clockHour12
+
     AuthUser:
       type: object
       properties:
@@ -1044,6 +1078,8 @@ components:
           oneOf:
             - $ref: "#/components/schemas/ClockStyle"
             - type: "null"
+        clockHour12:
+          type: ["boolean", "null"]
         avatarUrl:
           type: ["string", "null"]
         isActive:
@@ -1083,6 +1119,8 @@ components:
           oneOf:
             - $ref: "#/components/schemas/ClockStyle"
             - type: "null"
+        clockHour12:
+          type: ["boolean", "null"]
         avatarUrl:
           type: ["string", "null"]
         isActive: