feat: add Settings page with hijri seasons CRUD

- Server: seasons CRUD routes + generic NocoDB helpers
- Client: Settings page at /settings with inline add/edit/delete
- Seasons stored in NocoDB Seasons table
- Vite proxy: /api/seasons routed to Express server
- Nav links added (desktop + mobile)
- Locale keys for EN + AR
- Seasons loaded non-blocking on app mount

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/locales/en.json

@@ -12,6 +12,7 @@
     "comparison": "Comparison",
     "compare": "Compare",
     "slides": "Slides",
+    "settings": "Settings",
     "labels": "Labels",
     "labelsOn": "Labels On",
     "labelsOff": "Labels Off",
@@ -42,6 +43,8 @@
     "allChannels": "All Channels",
     "allMuseums": "All Events",
     "allQuarters": "All Quarters",
+    "season": "Season",
+    "allSeasons": "All Seasons",
     "reset": "Reset Filters"
   },
   "metrics": {
@@ -153,6 +156,18 @@
     "channel": "Channel",
     "captureRate": "Capture Rate"
   },
+  "settings": {
+    "title": "Settings",
+    "subtitle": "Configure dashboard settings and hijri seasons",
+    "seasons": "Hijri Seasons",
+    "seasonsHint": "Define seasons with their Gregorian date ranges. These appear as filter presets and chart overlays.",
+    "seasonName": "Season",
+    "startDate": "Start Date",
+    "endDate": "End Date",
+    "actions": "Actions",
+    "namePlaceholder": "e.g. Ramadan",
+    "add": "Add"
+  },
   "errors": {
     "config": "The dashboard is not configured. Please set up the ERP API connection.",
     "network": "Cannot reach the database server. Please check your internet connection.",