feat: 3-mode inspection with tabbed UI + batch upload

- Add batch inspection backend (multipart upload, SSE streaming, MongoDB)
- Add tabbed UI (single page / site crawling / batch upload) on home and history pages
- Add batch inspection progress, result pages with 2-panel layout
- Rename "사이트 전체" to "사이트 크롤링" across codebase
- Add python-multipart dependency for file upload
- Consolidate nginx SSE location for all inspection types

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/core/database.py

@@ -29,6 +29,11 @@ async def connect_db() -> None:
     await _db.site_inspections.create_index([("domain", 1), ("created_at", -1)])
     await _db.site_inspections.create_index([("created_at", -1)])
 
+    # Create indexes - batch_inspections
+    await _db.batch_inspections.create_index("batch_inspection_id", unique=True)
+    await _db.batch_inspections.create_index([("name", 1), ("created_at", -1)])
+    await _db.batch_inspections.create_index([("created_at", -1)])
+
     # Verify connection
     await _client.admin.command("ping")
     logger.info("MongoDB connected successfully: %s", settings.DB_NAME)