Initial commit: hardened DeerFlow factory

Vendored deer-flow upstream (bytedance/deer-flow) plus prompt-injection
hardening:

- New deerflow.security package: content_delimiter, html_cleaner,
  sanitizer (8 layers — invisible chars, control chars, symbols, NFC,
  PUA, tag chars, horizontal whitespace collapse with newline/tab
  preservation, length cap)
- New deerflow.community.searx package: web_search, web_fetch,
  image_search backed by a private SearX instance, every external
  string sanitized and wrapped in <<<EXTERNAL_UNTRUSTED_CONTENT>>>
  delimiters
- All native community web providers (ddg_search, tavily, exa,
  firecrawl, jina_ai, infoquest, image_search) replaced with hard-fail
  stubs that raise NativeWebToolDisabledError at import time, so a
  misconfigured tool.use path fails loud rather than silently falling
  back to unsanitized output
- Native client back-doors (jina_client.py, infoquest_client.py)
  stubbed too
- Native-tool tests quarantined under tests/_disabled_native/
  (collect_ignore_glob via local conftest.py)
- Sanitizer Layer 7 fix: only collapse horizontal whitespace, preserve
  newlines and tabs so list/table structure survives
- Hardened runtime config.yaml references only the searx-backed tools
- Factory overlay (backend/) kept in sync with deer-flow tree as a
  reference / source

See HARDENING.md for the full audit trail and verification steps.

deer-flow/frontend/tsconfig.json

@@ -0,0 +1,45 @@
+{
+  "compilerOptions": {
+    /* Base Options: */
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "target": "es2022",
+    "allowJs": true,
+    "resolveJsonModule": true,
+    "moduleDetection": "force",
+    "isolatedModules": true,
+    "verbatimModuleSyntax": true,
+    /* Strictness */
+    "strict": true,
+    "noUncheckedIndexedAccess": true,
+    "noImplicitAny": false,
+    "checkJs": false,
+    /* Bundled projects */
+    "lib": ["dom", "dom.iterable", "ES2022"],
+    "noEmit": true,
+    "module": "ESNext",
+    "moduleResolution": "Bundler",
+    "jsx": "react-jsx",
+    "plugins": [
+      {
+        "name": "next"
+      }
+    ],
+    "incremental": true,
+    /* Path Aliases */
+    "baseUrl": ".",
+    "paths": {
+      "@/*": ["./src/*"]
+    }
+  },
+  "include": [
+    "next-env.d.ts",
+    "**/*.ts",
+    "**/*.tsx",
+    "**/*.cjs",
+    "**/*.js",
+    ".next/types/**/*.ts",
+    ".next/dev/types/**/*.ts"
+  ],
+  "exclude": ["node_modules", "generated"]
+}