feat: Add pause/resume functionality to time tracking

Add pausedAt and pausedDuration columns to time_entries table.
New pause/resume endpoints with audit logging. Duration calculations
now correctly exclude paused time across start, stop, auto-stop,
and edit flows.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/routes/time-tracking.routes.js

@@ -30,6 +30,20 @@ router.post(
   timeTrackingController.stopTimeEntry
 );
 
+// Pause running time entry
+router.post(
+  '/:entryId/pause',
+  validateParams(z.object({ entryId: z.string().uuid() })),
+  timeTrackingController.pauseTimeEntry
+);
+
+// Resume paused time entry
+router.post(
+  '/:entryId/resume',
+  validateParams(z.object({ entryId: z.string().uuid() })),
+  timeTrackingController.resumeTimeEntry
+);
+
 // Get running time entry
 router.get('/running', timeTrackingController.getRunningTimeEntry);