feat(frontend): enhance API credentials system and build configuration

Add real API support in demo mode with credential checking, implement build-time version injection from package.json, and refactor update checking with 24-hour caching. Migrate landing page from Vue to Astro with comprehensive UI components including Hero, Features, Benefits, and Tech Stack sections. Update CI/CD workflow with expanded cache paths and security scanner version pinned.

landing/tsconfig.json

@@ -1,26 +1,11 @@
 {
+  "extends": "astro/tsconfigs/strictest",
   "compilerOptions": {
-    "target": "ES2020",
-    "useDefineForClassFields": true,
-    "module": "ESNext",
-    "lib": ["ES2020", "DOM", "DOM.Iterable"],
-    "skipLibCheck": true,
-    "moduleResolution": "bundler",
-    "allowImportingTsExtensions": true,
-    "resolveJsonModule": true,
-    "isolatedModules": true,
-    "noEmit": true,
-    "jsx": "preserve",
-    "strict": true,
-    "noUnusedLocals": true,
-    "noUnusedParameters": true,
-    "noFallthroughCasesInSwitch": true,
+    "jsx": "react-jsx",
+    "jsxImportSource": "react",
     "baseUrl": ".",
     "paths": {
-      "@/*": ["src/*"]
-    },
-    "types": ["vite/client"]
-  },
-  "include": ["src/**/*.ts", "src/**/*.tsx", "src/**/*.vue"],
-  "references": [{ "path": "./tsconfig.node.json" }]
-}
+      "@/*": ["./src/*"]
+    }
+  }
+}