feat: add finance/trading variant with market-focused dashboard

Add a new 'finance' site variant (finance.worldmonitor.app) following the
same pattern as the existing tech variant. Includes:

- Finance-specific RSS feeds: markets, forex, bonds, commodities, crypto,
  central banks, economic data, IPOs/M&A, derivatives, fintech, regulation,
  institutional investors, and market analysis (all free/open RSS sources)
- Finance-focused panels with trading-themed labels (Market Headlines,
  Live Markets, Forex & Currencies, Fixed Income, etc.)
- Geographic data for stock exchanges (30+), financial centers (20+),
  central banks (14), and commodity hubs (10) worldwide
- Four new map layers: stockExchanges, financialCenters, centralBanks,
  commodityHubs with tier-based icons and zoom-dependent labels
- Map popup rendering for all finance marker types
- Variant switcher updated with FINANCE tab in header
- Search modal with finance-specific sources and icons
- Vite HTML variant plugin metadata for SEO
- Build scripts (dev:finance, build:finance, test:e2e:finance)
- Tauri desktop config for Finance Monitor app

https://claude.ai/code/session_01CCmkws2EYuUHjYDonzXEtY

src-tauri/tauri.finance.conf.json

@@ -0,0 +1,30 @@
+{
+  "$schema": "https://schema.tauri.app/config/2",
+  "productName": "Finance Monitor",
+  "mainBinaryName": "finance-monitor",
+  "identifier": "app.worldmonitor.finance.desktop",
+  "app": {
+    "windows": [
+      {
+        "title": "Finance Monitor"
+      }
+    ]
+  },
+  "bundle": {
+    "shortDescription": "Finance Monitor desktop app",
+    "longDescription": "Finance Monitor desktop app for real-time markets and trading intelligence.",
+    "targets": [
+      "app",
+      "dmg",
+      "nsis",
+      "msi"
+    ],
+    "macOS": {
+      "hardenedRuntime": true
+    },
+    "windows": {
+      "digestAlgorithm": "sha256",
+      "timestampUrl": "https://timestamp.digicert.com"
+    }
+  }
+}