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/database/migrations/2026_03_09_003222_add_notes_to_actuals_table.php

@@ -0,0 +1,33 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Run the migrations.
+     */
+    public function up(): void
+    {
+        Schema::table('actuals', function (Blueprint $table) {
+            // Only add column if it doesn't exist (for databases that ran original migration before notes was added)
+            if (! Schema::hasColumn('actuals', 'notes')) {
+                $table->text('notes')->nullable()->after('hours_logged');
+            }
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::table('actuals', function (Blueprint $table) {
+            if (Schema::hasColumn('actuals', 'notes')) {
+                $table->dropColumn('notes');
+            }
+        });
+    }
+};