feat(programmer-tasks): loading states, confirmation & success dialogs

Day sheet dialogs (disapprove, justify): moved the async controller call
inside each dialog so loading state is owned there — button shows a
spinner and is disabled while the RPC is in flight; errors display inline
instead of via a snackbar after dialog close.

Detail screen (approve): added _approvingSheet bool; Approve button shows
CircularProgressIndicator while in flight. On success shows an AlertDialog
"Sheet Approved" with a check icon instead of silently updating state.

Approvals tab (bulk approve): upgraded post-approve feedback from a
snackbar to a success AlertDialog showing the count of approved sheets
and any skipped ones.

Day sheets tab (submit): added confirmation AlertDialog before the
existing submit flow so programmers don't accidentally submit mid-day.

Co-Authored-By: claude-flow <ruv@ruv.net>

lib/screens/programmer_tasks/day_sheets/approvals_tab.dart

@@ -87,12 +87,27 @@ class _ApprovalsTabState extends ConsumerState<ApprovalsTab> {
         _approving = false;
       });
 
-      final buf = StringBuffer('Approved ${result.approvedIds.length}');
-      if (result.skippedIds.isNotEmpty) {
-        buf.write(', ${result.skippedIds.length} already reviewed');
-      }
-      ScaffoldMessenger.of(context)
-          .showSnackBar(SnackBar(content: Text(buf.toString())));
+      final count = result.approvedIds.length;
+      final skipped = result.skippedIds.length;
+      await showDialog<void>(
+        context: context,
+        builder: (ctx) => AlertDialog(
+          icon: const Icon(Icons.check_circle_outline, size: 48),
+          title: Text('Approved $count ${count == 1 ? 'Sheet' : 'Sheets'}'),
+          content: skipped > 0
+              ? Text(
+                  '$skipped ${skipped == 1 ? 'sheet was' : 'sheets were'} '
+                  'already reviewed and skipped.',
+                )
+              : null,
+          actions: [
+            FilledButton(
+              onPressed: () => Navigator.of(ctx).pop(),
+              child: const Text('Done'),
+            ),
+          ],
+        ),
+      );
     } on DaySheetActionException catch (e) {
       if (!mounted) return;
       setState(() => _approving = false);