feat: Phase 1 - Redis config, Dashboard cache, Report cache, N+1 fixes, observers

- Add predis/predis for Redis support
- Configure cache/queue defaults to redis in config + .env.example
- Create DashboardController with 60s cache for dashboard queries
- Add cache (5min) to ReportController::generate() and preview()
- Add FeatureObserver, InspectionObserver, IssueObserver for cache invalidation
- Fix N+1 in ProjectMap (eager load template, images), TaskManager (subtasks.parentTask)
- Register observers in AppServiceProvider

Tests: 101 passing (319 assertions)

app/Observers/FeatureObserver.php

@@ -0,0 +1,26 @@
+<?php
+
+namespace App\Observers;
+
+use App\Models\Feature;
+use Illuminate\Support\Facades\Cache;
+
+class FeatureObserver
+{
+    public function saved(Feature $feature): void
+    {
+        $this->clearReportCache($feature->project_id);
+    }
+
+    public function deleted(Feature $feature): void
+    {
+        $this->clearReportCache($feature->project_id);
+    }
+
+    private function clearReportCache(?int $projectId): void
+    {
+        if ($projectId) {
+            Cache::tags(["report:project:{$projectId}"])->flush();
+        }
+    }
+}