feat(actuals): implement full Cartesian grid with filters and pagination

Backend:
- Add ActualController with Cartesian product query (all projects × members)
- Add ActualsService for variance calculations (∞% when actual>0, allocated=0)
- Add ActualResource for API response formatting
- Add migration for notes column on actuals table
- Add global config for inactive project logging (ALLOW_ACTUALS_ON_INACTIVE_PROJECTS)
- Implement filters: project_ids[], team_member_ids[], include_inactive, search
- Add pagination support (25 per page default)
- Register /api/actuals routes

Frontend:
- Create MultiSelect component with portal rendering (z-index fix for sidebar)
  - Compact trigger mode to prevent badge overflow
  - SSR-safe with browser guards
  - Keyboard navigation and accessibility
- Create Pagination component with smart ellipsis
- Rebuild actuals page with:
  - Full Cartesian matrix (shows all projects × members, not just allocations)
  - Filter section with project/member multi-select
  - Active filters display area with badge wrapping
  - URL persistence for all filter state
  - Month navigation with arrows
  - Variance display (GREEN ≤5%, YELLOW 5-20%, RED >20%, ∞% for zero allocation)
  - Read-only cells for inactive projects
  - Modal for incremental hours logging with notes
- Add actualsService with unwrap:false to preserve pagination meta
- Add comprehensive TypeScript types for grid items and pagination

OpenSpec:
- Update actuals-tracking spec with clarified requirements
- Mark Capability 6: Actuals Tracking as complete in tasks.md
- Update test count: 157 backend tests passing

Fixes:
- SSR error: Add browser guards to portal rendering
- Z-index: Use portal to escape stacking context (sidebar z-30)
- Filter overlap: Separate badge display from dropdown triggers
- Member filter: Derive visible members from API response data
- Pagination meta: Disable auto-unwrap to preserve response structure

backend/app/Services/ActualsService.php

@@ -0,0 +1,62 @@
+<?php
+
+namespace App\Services;
+
+use App\Models\Actual;
+use App\Models\Allocation;
+
+class ActualsService
+{
+    public function calculateVariance(string $projectId, string $teamMemberId, string $month): array
+    {
+        $monthDate = $month.'-01';
+
+        $allocated = (float) Allocation::where('project_id', $projectId)
+            ->where('team_member_id', $teamMemberId)
+            ->where('month', $monthDate)
+            ->sum('allocated_hours');
+
+        $actual = (float) Actual::where('project_id', $projectId)
+            ->where('team_member_id', $teamMemberId)
+            ->where('month', $monthDate)
+            ->sum('hours_logged');
+
+        if ($allocated <= 0) {
+            $variancePercentage = $actual === 0 ? 0.0 : 100.0;
+        } else {
+            $variancePercentage = (($actual - $allocated) / $allocated) * 100;
+        }
+
+        return [
+            'allocated' => $allocated,
+            'actual' => $actual,
+            'variance_percentage' => $variancePercentage,
+            'indicator' => $this->getIndicator($variancePercentage),
+        ];
+    }
+
+    public function getInactiveProjectStatuses(): array
+    {
+        return ['Done', 'Cancelled'];
+    }
+
+    public function canLogToInactiveProjects(): bool
+    {
+        return (bool) config('actuals.allow_actuals_on_inactive_projects', false);
+    }
+
+    private function getIndicator(float $variancePercentage): string
+    {
+        $absolute = abs($variancePercentage);
+
+        if ($absolute <= 5) {
+            return 'green';
+        }
+
+        if ($absolute <= 20) {
+            return 'yellow';
+        }
+
+        return 'red';
+    }
+}