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/day_sheets_tab.dart

@@ -43,6 +43,26 @@ class _DaySheetsTabState extends ConsumerState<DaySheetsTab> {
   // ---------------------------------------------------------------------------
 
   Future<void> _submit(DateTime today) async {
+    final ok = await showDialog<bool>(
+      context: context,
+      builder: (ctx) => AlertDialog(
+        title: const Text("Submit today's work?"),
+        content: const Text(
+            "This will send your day sheet to admin for review."),
+        actions: [
+          TextButton(
+            onPressed: () => Navigator.of(ctx).pop(false),
+            child: const Text('Cancel'),
+          ),
+          FilledButton(
+            onPressed: () => Navigator.of(ctx).pop(true),
+            child: const Text('Submit'),
+          ),
+        ],
+      ),
+    );
+    if (ok != true) return;
+
     setState(() => _submitting = true);
     try {
       await ref.read(daySheetsControllerProvider).submit(today);