🔗 Add URL Content Extraction Feature (#514)

* feat: add URL content extraction for AI diagram generation

* Changes made as recommended by Claude:

1. Added a request timeout to prevent server resources from being tied up (route.ts)
2. Implemented runtime validation for the API response shape (url-utils.ts)
3. Removed hardcoded English error messages and replaced them with localized strings (url-input-dialog.tsx)
4. Fixed the incorrect i18n namespace (changed from pdf.* to url.*) (url-input-dialog.tsx and en/ja/zh.json)

* chore: restore package.json and package-lock.json

* fix: use i18n strings for URL dialog error messages

---------

Co-authored-by: dayuan.jiang <jdy.toh@gmail.com>

package.json

@@ -40,6 +40,7 @@
         "@ai-sdk/react": "^3.0.1",
         "@aws-sdk/client-dynamodb": "^3.957.0",
         "@aws-sdk/credential-providers": "^3.943.0",
+        "@extractus/article-extractor": "^8.0.18",
         "@formatjs/intl-localematcher": "^0.7.2",
         "@langfuse/client": "^4.4.9",
         "@langfuse/otel": "^4.4.4",
@@ -87,6 +88,7 @@
         "sonner": "^2.0.7",
         "tailwind-merge": "^3.0.2",
         "tailwindcss-animate": "^1.0.7",
+        "turndown": "^7.2.0",
         "unpdf": "^1.4.0",
         "zod": "^4.1.12"
     },
@@ -115,6 +117,7 @@
         "@types/pako": "^2.0.3",
         "@types/react": "^19",
         "@types/react-dom": "^19",
+        "@types/turndown": "^5.0.6",
         "@vitejs/plugin-react": "^5.1.2",
         "@vitest/coverage-v8": "^4.0.16",
         "concurrently": "^9.2.1",