feat(chat): 聊天页支持日历定位/卡片解析/HTML导出分页

- 新增 /api/chat/messages/daily_counts 与 /api/chat/messages/anchor，用于月度热力图与按日/首条定位\n- messages/around 支持跨 message 分片定位，定位更稳定\n- 新增 /api/chat/chat_history/resolve 与 /api/chat/appmsg/resolve，合并转发/链接卡片可按 server_id 补全\n- 新增 /api/chat/media/favicon，并补齐 link 本地缩略图处理\n- HTML 导出支持分页加载（html_page_size），避免大聊天单文件卡顿\n- tests: 覆盖 heatmap/anchor、favicon 缓存、HTML 分页导出

tests/test_chat_media_favicon.py

@@ -0,0 +1,133 @@
+import os
+import sqlite3
+import sys
+import unittest
+import importlib
+from pathlib import Path
+from tempfile import TemporaryDirectory
+from unittest.mock import patch
+
+
+ROOT = Path(__file__).resolve().parents[1]
+sys.path.insert(0, str(ROOT / "src"))
+
+
+class _FakeResponse:
+    def __init__(self, *, status_code: int = 200, headers: dict | None = None, url: str = "", body: bytes = b""):
+        self.status_code = int(status_code)
+        self.headers = dict(headers or {})
+        self.url = str(url or "")
+        self._body = bytes(body or b"")
+
+    def iter_content(self, chunk_size: int = 64 * 1024):
+        yield self._body
+
+    def close(self) -> None:
+        return None
+
+
+class TestChatMediaFavicon(unittest.TestCase):
+    def test_chat_media_favicon_caches(self):
+        from fastapi import FastAPI
+        from fastapi.testclient import TestClient
+
+        # 1x1 PNG (same as other avatar cache tests)
+        png = bytes.fromhex(
+            "89504E470D0A1A0A"
+            "0000000D49484452000000010000000108060000001F15C489"
+            "0000000D49444154789C6360606060000000050001A5F64540"
+            "0000000049454E44AE426082"
+        )
+
+        with TemporaryDirectory() as td:
+            root = Path(td)
+
+            prev_data = None
+            prev_cache = None
+            try:
+                prev_data = os.environ.get("WECHAT_TOOL_DATA_DIR")
+                prev_cache = os.environ.get("WECHAT_TOOL_AVATAR_CACHE_ENABLED")
+                os.environ["WECHAT_TOOL_DATA_DIR"] = str(root)
+                os.environ["WECHAT_TOOL_AVATAR_CACHE_ENABLED"] = "1"
+
+                import wechat_decrypt_tool.app_paths as app_paths
+                import wechat_decrypt_tool.avatar_cache as avatar_cache
+                import wechat_decrypt_tool.routers.chat_media as chat_media
+
+                importlib.reload(app_paths)
+                importlib.reload(avatar_cache)
+                importlib.reload(chat_media)
+
+                def fake_head(url, **_kwargs):
+                    # Pretend short-link resolves to bilibili.
+                    return _FakeResponse(
+                        status_code=200,
+                        headers={},
+                        url="https://www.bilibili.com/video/BV1Au4tzNEq2",
+                        body=b"",
+                    )
+
+                def fake_get(url, **_kwargs):
+                    u = str(url or "")
+                    if "www.bilibili.com/favicon.ico" in u:
+                        return _FakeResponse(
+                            status_code=200,
+                            headers={"Content-Type": "image/png", "content-length": str(len(png))},
+                            url=u,
+                            body=png,
+                        )
+                    return _FakeResponse(
+                        status_code=404,
+                        headers={"Content-Type": "text/html"},
+                        url=u,
+                        body=b"",
+                    )
+
+                app = FastAPI()
+                app.include_router(chat_media.router)
+                client = TestClient(app)
+
+                with patch("wechat_decrypt_tool.routers.chat_media.requests.head", side_effect=fake_head) as mock_head, patch(
+                    "wechat_decrypt_tool.routers.chat_media.requests.get", side_effect=fake_get
+                ) as mock_get:
+                    resp = client.get("/api/chat/media/favicon", params={"url": "https://b23.tv/au68guF"})
+                    self.assertEqual(resp.status_code, 200)
+                    self.assertTrue(resp.headers.get("content-type", "").startswith("image/"))
+                    self.assertEqual(resp.content, png)
+
+                    # Second call should hit disk cache (no extra favicon download).
+                    resp2 = client.get("/api/chat/media/favicon", params={"url": "https://b23.tv/au68guF"})
+                    self.assertEqual(resp2.status_code, 200)
+                    self.assertEqual(resp2.content, png)
+
+                    self.assertGreaterEqual(mock_head.call_count, 1)
+                    self.assertEqual(mock_get.call_count, 1)
+
+                cache_db = root / "output" / "avatar_cache" / "favicon" / "avatar_cache.db"
+                self.assertTrue(cache_db.exists())
+
+                conn = sqlite3.connect(str(cache_db))
+                try:
+                    row = conn.execute(
+                        "SELECT source_kind, source_url, media_type FROM avatar_cache_entries WHERE source_kind = 'url' LIMIT 1"
+                    ).fetchone()
+                    self.assertIsNotNone(row)
+                    self.assertEqual(str(row[0] or ""), "url")
+                    self.assertIn("favicon.ico", str(row[1] or ""))
+                    self.assertTrue(str(row[2] or "").startswith("image/"))
+                finally:
+                    conn.close()
+            finally:
+                if prev_data is None:
+                    os.environ.pop("WECHAT_TOOL_DATA_DIR", None)
+                else:
+                    os.environ["WECHAT_TOOL_DATA_DIR"] = prev_data
+                if prev_cache is None:
+                    os.environ.pop("WECHAT_TOOL_AVATAR_CACHE_ENABLED", None)
+                else:
+                    os.environ["WECHAT_TOOL_AVATAR_CACHE_ENABLED"] = prev_cache
+
+
+if __name__ == "__main__":
+    unittest.main()
+