feat: add video OCR/ASR, DOCX/PDF export, input block and risk config updates

- Video pipeline: video file OCR via VLM plus audio track ASR, integrated
  into job_handlers with progress emit per phase. New media_utils.py for
  audio extraction from video files.
- Document export: richExport.js replaces inline docx builder; DOCX and PDF
  export buttons are now enabled in MilkdownEditor. File size limit raised to
  100 MB.
- Input block: new InputBlockCrepe.vue component with inputBlockPlugin.ts
  and inputBlock.js for custom user-input nodes in the editor.
- Risk config: added Vite dev server ports (5173) to CORS allowlist and
  increased OCR max input from 10 MB to 100 MB.
- TTS/ASR refactor: simplified tts_asr.py model loading and warmup logic.
- Test coverage: updated tests for llm, main endpoints, pro completions and
  web search modules.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/media_utils.py

@@ -0,0 +1,47 @@
+from __future__ import annotations
+
+import os
+import subprocess
+import tempfile
+
+
+VIDEO_EXTENSIONS = {".mp4", ".webm", ".mov", ".avi", ".mkv", ".m4v", ".ogv"}
+
+
+def is_video_filename(filename: str = "", mime_type: str = "") -> bool:
+    ext = os.path.splitext(filename or "")[1].lower()
+    mime = (mime_type or "").strip().lower()
+    return ext in VIDEO_EXTENSIONS or mime.startswith("video/")
+
+
+def extract_audio_wav_bytes(input_path: str) -> bytes:
+    if not input_path or not os.path.exists(input_path):
+        raise FileNotFoundError("输入媒体文件不存在")
+
+    fd, output_path = tempfile.mkstemp(suffix=".wav")
+    os.close(fd)
+    try:
+        subprocess.run(
+            [
+                "ffmpeg",
+                "-y",
+                "-i",
+                input_path,
+                "-vn",
+                "-acodec",
+                "pcm_s16le",
+                "-ar",
+                "16000",
+                "-ac",
+                "1",
+                output_path,
+            ],
+            check=True,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+        )
+        with open(output_path, "rb") as handle:
+            return handle.read()
+    finally:
+        if os.path.exists(output_path):
+            os.unlink(output_path)