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/app/Services/ProjectService.php

@@ -96,6 +96,7 @@ class ProjectService
             'title' => 'sometimes|string|max:255',
             'type_id' => 'sometimes|integer|exists:project_types,id',
             'status_id' => 'sometimes|integer|exists:project_statuses,id',
+            'approved_estimate' => 'sometimes|numeric|min:0',
         ], [
             'code.unique' => 'Project code must be unique',
         ]);