feat: scan reads prompts embedded in videos; unreadable files no longer log errors

The output scan handed every .mp4 to Pillow and logged one ERROR per file.
ComfyUI's video savers store the queued graph as JSON in the container's
comment tag, so those files carry prompts worth linking.

- utils/video_metadata.py reads the comment/description tag through
  ffprobe with a timeout, normalised to the PNG text-chunk shape so the
  existing parser handles both; without ffprobe videos are skipped and a
  single INFO notice is logged
- _extract_comfyui_metadata routes videos there and logs unreadable images
  as warnings, since the scan carries on past them

Test hygiene: every aiohttp test base class overrode tearDownAsync without
calling super(), so no test client was ever closed. That produced thousands
of ResourceWarnings, "Unclosed client session" errors from asyncio that
broke log assertions, and doubled the suite's run time.

tests/test_api_admin.py

@@ -69,6 +69,7 @@ class AdminAPITestCase(AioHTTPTestCase):
         return app
 
     async def tearDownAsync(self):
+        await super().tearDownAsync()  # closes the aiohttp test client
         GalleryConfig.MONITORING_DIRECTORIES = self._orig_gallery_dirs
         PromptManagerConfig.update_config(self._orig_pm_config)
         for key, value in self._orig_env.items():
@@ -1703,5 +1704,89 @@ class TestWorkerThreadsSetting(AdminAPITestCase):
         self.assertIn('"added": 1', body)
 
 
+def _write_mp4(path, comment):
+    """Tiny black video with ``comment`` in its container tags (needs ffmpeg)."""
+    import subprocess
+
+    subprocess.run(
+        [
+            "ffmpeg",
+            "-v",
+            "quiet",
+            "-f",
+            "lavfi",
+            "-i",
+            "color=c=black:s=16x16:d=0.2",
+            "-metadata",
+            f"comment={comment}",
+            "-y",
+            str(path),
+        ],
+        check=True,
+        timeout=60,
+    )
+
+
+class TestScanReadsVideos(AdminAPITestCase):
+    """Videos saved by ComfyUI carry the graph in their comment tag."""
+
+    def setUp(self):
+        super().setUp()
+        from utils import video_metadata
+
+        video_metadata.ffprobe_path.cache_clear()
+        self.addCleanup(video_metadata.ffprobe_path.cache_clear)
+
+    @unittest.skipUnless(
+        shutil.which("ffmpeg") and shutil.which("ffprobe"), "ffmpeg not installed"
+    )
+    async def test_scan_adds_prompts_found_in_videos(self):
+        graph = {"1": {"class_type": "CLIPTextEncode", "inputs": {"text": "a cat"}}}
+        _write_mp4(
+            self.output_dir / "clip.mp4", json.dumps({"prompt": json.dumps(graph)})
+        )
+        GalleryConfig.MONITORING_DIRECTORIES = [str(self.output_dir)]
+
+        with self.assertNoLogs(level="ERROR"):
+            body = await (
+                await self.client.request("POST", "/prompt_manager/scan")
+            ).text()
+
+        self.assertIn('"added": 1', body)
+        prompts = self.api.db.get_recent_prompts(limit=10)["prompts"]
+        self.assertEqual([p["text"] for p in prompts], ["a cat"])
+        images = self.api.db.get_prompt_images(prompts[0]["id"])
+        self.assertTrue(images[0]["image_path"].endswith("clip.mp4"))
+
+    async def test_scan_without_ffprobe_skips_videos_quietly(self):
+        from unittest.mock import patch
+        from utils import video_metadata
+
+        (self.output_dir / "clip.mp4").write_bytes(b"\x00\x00\x00\x18ftypisom")
+        GalleryConfig.MONITORING_DIRECTORIES = [str(self.output_dir)]
+
+        with patch.object(video_metadata.shutil, "which", return_value=None):
+            with self.assertNoLogs("prompt_manager", level="WARNING"):
+                body = await (
+                    await self.client.request("POST", "/prompt_manager/scan")
+                ).text()
+
+        self.assertIn('"processed": 1', body)
+        self.assertIn('"found": 0', body)
+
+    async def test_unreadable_image_is_a_warning_not_an_error(self):
+        (self.output_dir / "bad.png").write_bytes(b"\x89PNG not really")
+        GalleryConfig.MONITORING_DIRECTORIES = [str(self.output_dir)]
+
+        with self.assertLogs(level="WARNING") as cm:
+            body = await (
+                await self.client.request("POST", "/prompt_manager/scan")
+            ).text()
+
+        self.assertIn('"type": "complete"', body)
+        self.assertTrue(any("bad.png" in line for line in cm.output))
+        self.assertEqual([line for line in cm.output if line.startswith("ERROR")], [])
+
+
 if __name__ == "__main__":
     unittest.main()