feat: add 9 new dashboard features with export and comparison

- Add Hidden Champions tab with filterable product table
- Add Opportunity Map tab with scatter chart (supply/demand quadrants)
- Add Sales Funnel section to Overview with conversion rates
- Add Price Distribution histogram with mean/median lines
- Add Competition Score gauge (0-100) with 4 sub-metrics
- Add Excel export (3-sheet xlsx) and Print buttons to dashboard
- Add Report Comparison page with KPI diff table and brand bar chart
- Add enrichment UI to ReportList with progress tracking
- Add sidebar navigation with Karşılaştır route
- Refactor UI: Layout, Sidebar, TopBar, KpiCard, SkeletonLoader components
- Improve drill-down UX with visible pill buttons and tooltips

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

reports/mart_kozmetik_raporu_20260307_163635.json

@@ -0,0 +1,16 @@
+{
+  "report_name": "Mart Kozmetik Raporu",
+  "category": "Kozmetik",
+  "created_at": "2026-03-07T16:36:35.817598",
+  "total_subcategories": 1,
+  "total_products": 100,
+  "details": [
+    {
+      "category_id": 85,
+      "category_name": "Cilt Bakımı",
+      "success": true,
+      "total_products": 100,
+      "file_path": "../categories/Cilt_Bakımı_85.json"
+    }
+  ]
+}