feat: add Mihomo API client with refresh polling

Implements MihomoClient wrapping Mihomo's REST API with provider refresh
polling, config reload, and startup readiness check. Also fixes a
Python 3.14 + respx 0.21.1 compatibility issue where the httpcore mocker
passes bytes method to httpx.Request causing Method pattern matching to
fail; resolved by switching respx DEFAULT_MOCKER to the httpx-level mocker.

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

app/mihomo.py

@@ -0,0 +1,69 @@
+import asyncio
+import logging
+
+import httpx
+
+logger = logging.getLogger(__name__)
+
+
+class MihomoClient:
+    def __init__(self, base_url: str, secret: str):
+        self._base_url = base_url.rstrip("/")
+        self._headers = {"Authorization": f"Bearer {secret}"} if secret else {}
+
+    async def trigger_provider_refresh(self, name: str) -> None:
+        async with httpx.AsyncClient() as c:
+            resp = await c.put(
+                f"{self._base_url}/providers/proxies/{name}",
+                headers=self._headers,
+                timeout=10.0,
+            )
+            resp.raise_for_status()
+
+    async def get_provider(self, name: str) -> dict:
+        async with httpx.AsyncClient() as c:
+            resp = await c.get(
+                f"{self._base_url}/providers/proxies/{name}",
+                headers=self._headers,
+                timeout=10.0,
+            )
+            resp.raise_for_status()
+            return resp.json()
+
+    async def refresh_and_collect(self, name: str, timeout: int = 30) -> list[dict]:
+        initial = await self.get_provider(name)
+        initial_ts = initial.get("updatedAt", "")
+
+        await self.trigger_provider_refresh(name)
+
+        loop = asyncio.get_event_loop()
+        deadline = loop.time() + timeout
+        while loop.time() < deadline:
+            await asyncio.sleep(1)
+            data = await self.get_provider(name)
+            if data.get("updatedAt", "") != initial_ts:
+                return data.get("proxies", [])
+
+        raise TimeoutError(f"Provider {name!r} did not refresh within {timeout}s")
+
+    async def reload_config(self) -> None:
+        async with httpx.AsyncClient() as c:
+            resp = await c.put(
+                f"{self._base_url}/configs",
+                json={},
+                headers=self._headers,
+                timeout=10.0,
+            )
+            resp.raise_for_status()
+
+    async def wait_ready(self, retries: int = 60) -> None:
+        for i in range(retries):
+            try:
+                async with httpx.AsyncClient() as c:
+                    resp = await c.get(f"{self._base_url}/version", timeout=3.0)
+                    resp.raise_for_status()
+                    return
+            except Exception:
+                logger.info("Waiting for Mihomo... (%d/%d)", i + 1, retries)
+                await asyncio.sleep(1)
+        raise RuntimeError("Mihomo did not become available")