Add milestone data layer and redesign Projects tab

Milestone data layer:
- lib/data/models/milestone.dart: Milestone model with progress fields
  (total, completed, pct) from backend progress endpoint
- lib/data/api/milestones_api.dart: CRUD client for
  /api/projects/:id/milestones
- lib/data/repositories/milestones_repository.dart: thin repository wrapper
- lib/providers/milestones_provider.dart: FutureProvider.family keyed by
  project ID — lazily fetched per project when expanded
- api_client_provider.dart: registers milestonesApiProvider and
  milestonesRepositoryProvider

Projects tab redesign (project_list_screen.dart):
- Each project is now an ExpansionTile showing open task count in subtitle
- Expanding a project fetches its milestones and groups tasks under milestone
  headers with inline progress bar (completed/total count)
- Tasks show status icon, due date with overdue highlighting, priority dot
- 'No milestone' section at bottom for unassigned tasks
- Tapping a task navigates to the task editor
- Long-press on project title opens archive/complete/delete bottom sheet
- 'New task' button at bottom of each expanded project section

Bump version to 26.03.02+1

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/providers/api_client_provider.dart

@@ -5,12 +5,14 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import '../data/api/api_client.dart';
 import '../data/api/auth_api.dart';
 import '../data/api/chat_api.dart';
+import '../data/api/milestones_api.dart';
 import '../data/api/notes_api.dart';
 import '../data/api/projects_api.dart';
 import '../data/api/quick_capture_api.dart';
 import '../data/api/tasks_api.dart';
 import '../data/repositories/auth_repository.dart';
 import '../data/repositories/chat_repository.dart';
+import '../data/repositories/milestones_repository.dart';
 import '../data/repositories/notes_repository.dart';
 import '../data/repositories/projects_repository.dart';
 import '../data/repositories/tasks_repository.dart';
@@ -70,3 +72,11 @@ final chatRepositoryProvider = Provider<ChatRepository>((ref) {
 final projectsRepositoryProvider = Provider<ProjectsRepository>((ref) {
   return ProjectsRepository(ref.watch(projectsApiProvider));
 });
+
+final milestonesApiProvider = Provider<MilestonesApi>((ref) {
+  return MilestonesApi(ref.watch(dioProvider));
+});
+
+final milestonesRepositoryProvider = Provider<MilestonesRepository>((ref) {
+  return MilestonesRepository(ref.watch(milestonesApiProvider));
+});

lib/providers/milestones_provider.dart

@@ -0,0 +1,11 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+import '../data/models/milestone.dart';
+import 'api_client_provider.dart';
+
+/// Fetches active milestones for a given project ID.
+/// Keyed by projectId so each project gets its own cached list.
+final projectMilestonesProvider =
+    FutureProvider.family<List<Milestone>, int>((ref, projectId) {
+  return ref.watch(milestonesRepositoryProvider).getAll(projectId);
+});