feat(backend): enhance allocation and project management

Update controllers and services for allocation fidelity:
- AllocationController: variance data in responses, bulk operations
- ProjectController: include plan data in responses
- ProjectMonthPlanController: planning grid API
- AllocationMatrixService: support untracked allocations
- ProjectResource/TeamMemberResource: include reconciliation data

Improved test coverage for allocation flows.

backend/tests/Unit/AllocationCacheInvalidationTest.php

@@ -7,6 +7,7 @@ use App\Models\Project;
 use App\Models\Role;
 use App\Models\TeamMember;
 use App\Services\AllocationMatrixService;
+use App\Services\VarianceCalculator;
 use Illuminate\Foundation\Testing\RefreshDatabase;
 use Tests\TestCase;
 
@@ -24,11 +25,11 @@ class AllocationCacheInvalidationTest extends TestCase
         Allocation::factory()->create([
             'project_id' => $project->id,
             'team_member_id' => $teamMember->id,
-            'month' => '2026-02',
+            'month' => '2026-02-01',
             'allocated_hours' => 40,
         ]);
 
-        $matrixService = new AllocationMatrixService;
+        $matrixService = new AllocationMatrixService(new VarianceCalculator);
         $result = $matrixService->getMatrix('2026-02');
 
         $this->assertArrayHasKey('allocations', $result);