feat: add MCP Apps example servers module

Wire up 13 MCP Apps servers from the @modelcontextprotocol/server-* packages:
- budget-allocator: Interactive budget allocation UI
- cohort-heatmap: Customer retention heatmap
- customer-segmentation: Scatter chart with clustering
- map: Interactive 3D globe viewer (CesiumJS)
- pdf: Interactive PDF viewer
- scenario-modeler: SaaS business projections dashboard
- shadertoy: Real-time GLSL shader renderer
- sheet-music: ABC notation to sheet music visualizer
- system-monitor: Real-time OS metrics display
- threejs: 3D scene renderer
- transcript: Live speech transcription
- video-resource: Binary video streaming via MCP resources
- wiki-explorer: Wikipedia link graph visualization

Each server is mounted at /{slug}/mcp and shares the same OAuth
authentication as the main MCP server.

Also updates the splash page to dynamically list all available
example servers.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

package.json

@@ -25,6 +25,19 @@
   "dependencies": {
     "@modelcontextprotocol/ext-apps": "^0.4.0",
     "@modelcontextprotocol/sdk": "^1.24.2",
+    "@modelcontextprotocol/server-budget-allocator": "^0.4.1",
+    "@modelcontextprotocol/server-cohort-heatmap": "^0.4.1",
+    "@modelcontextprotocol/server-customer-segmentation": "^0.4.1",
+    "@modelcontextprotocol/server-map": "^0.4.1",
+    "@modelcontextprotocol/server-pdf": "^0.4.1",
+    "@modelcontextprotocol/server-scenario-modeler": "^0.4.1",
+    "@modelcontextprotocol/server-shadertoy": "^0.4.1",
+    "@modelcontextprotocol/server-sheet-music": "^0.4.1",
+    "@modelcontextprotocol/server-system-monitor": "^0.4.1",
+    "@modelcontextprotocol/server-threejs": "^0.4.1",
+    "@modelcontextprotocol/server-transcript": "^0.4.1",
+    "@modelcontextprotocol/server-video-resource": "^0.4.1",
+    "@modelcontextprotocol/server-wiki-explorer": "^0.4.1",
     "@redis/client": "^1.6.0",
     "cors": "^2.8.5",
     "dotenv": "^16.4.7",
@@ -59,7 +72,7 @@
     "@types/express-serve-static-core": "^5.0.2"
   },
   "engines": {
-    "node": ">=16"
+    "node": ">=20.16.0 || >=22.3.0"
   },
   "author": "",
   "license": "MIT"