Add server-side /api/rescan upload pipeline and Home UI.

Accept ZIP/single help files, process with help_processor into OUTPUT_DIR+Postgres, pollable jobs, optional RESCAN_TOKEN.

Co-authored-by: Cursor <cursoragent@cursor.com>

requirements-webapp.txt

@@ -3,3 +3,13 @@ uvicorn[standard]>=0.27.0
 jinja2>=3.1.0
 psycopg2-binary>=2.9.9
 pydantic>=2.0.0
+python-multipart>=0.0.9
+
+# help_processor (server-side rescan)
+anthropic>=0.25.0
+python-docx>=1.1.0
+beautifulsoup4>=4.12.0
+lxml>=5.0.0
+pdfplumber>=0.11.0
+chardet>=5.0.0
+Pillow>=10.0.0