Mejoras de estabilidad de stream IPTV y nuevo registro de fallos

- restream.py: eliminar -reconnect_streamed de ffmpeg para evitar rebobinados
  al reconectar (el proveedor re-enviaba desde keyframe anterior causando PTS
  backward). El loop de Python gestiona las reconexiones con conexión fresca.
- restream.py: eliminar _drain_queue del loop de reconexión para que el buffer
  de la cola cubra el tiempo de reconexión sin pantalla negra en el player.
- restream.py: añadir buffer_server_bytes/secs/capacity a stats() y método
  _log_stream_event() para persistir eventos de caída y recuperación en BD.
- models/stream_event.py: nuevo modelo StreamEvent para registro de fallos.
- database.py: registrar StreamEvent en init_db.
- api/admin/logs.py: nuevos endpoints GET/DELETE /logs/events.
- Dashboard.tsx: mostrar reserva de buffer del servidor (capacidad + estado).
- Logs.tsx: añadir pestaña "Fallos de stream" con tabla de eventos persistidos.

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

backend/core/xtream_client.py

@@ -0,0 +1,87 @@
+"""Client for consuming Xtream Codes API from provider."""
+import aiohttp
+import asyncio
+from typing import Any
+import logging
+
+logger = logging.getLogger(__name__)
+
+
+class XtreamClient:
+    def __init__(self, base_url: str, username: str, password: str):
+        self.base_url = base_url.rstrip("/")
+        self.username = username
+        self.password = password
+
+    def _api_url(self) -> str:
+        return f"{self.base_url}/player_api.php"
+
+    async def _get(self, params: dict) -> Any:
+        params = {"username": self.username, "password": self.password, **params}
+        timeout = aiohttp.ClientTimeout(total=30)
+        async with aiohttp.ClientSession(timeout=timeout) as session:
+            async with session.get(self._api_url(), params=params, ssl=False) as resp:
+                resp.raise_for_status()
+                return await resp.json(content_type=None)
+
+    async def get_user_info(self) -> dict:
+        return await self._get({})
+
+    async def get_live_categories(self) -> list[dict]:
+        return await self._get({"action": "get_live_categories"})
+
+    async def get_live_streams(self, category_id: str | None = None) -> list[dict]:
+        params = {"action": "get_live_streams"}
+        if category_id:
+            params["category_id"] = category_id
+        return await self._get(params)
+
+    async def get_vod_categories(self) -> list[dict]:
+        return await self._get({"action": "get_vod_categories"})
+
+    async def get_vod_streams(self, category_id: str | None = None) -> list[dict]:
+        params = {"action": "get_vod_streams"}
+        if category_id:
+            params["category_id"] = category_id
+        return await self._get(params)
+
+    async def get_series_categories(self) -> list[dict]:
+        return await self._get({"action": "get_series_categories"})
+
+    async def get_series(self, category_id: str | None = None) -> list[dict]:
+        params = {"action": "get_series"}
+        if category_id:
+            params["category_id"] = category_id
+        return await self._get(params)
+
+    async def get_series_info(self, series_id: str) -> dict:
+        return await self._get({"action": "get_series_info", "series_id": series_id})
+
+    async def get_vod_info(self, vod_id: str) -> dict:
+        return await self._get({"action": "get_vod_info", "vod_id": vod_id})
+
+    async def get_epg(self, stream_id: str | None = None) -> dict:
+        params = {"action": "get_short_epg"}
+        if stream_id:
+            params["stream_id"] = stream_id
+        return await self._get(params)
+
+    def build_live_stream_url(self, stream_id: str, ext: str = "ts") -> str:
+        return f"{self.base_url}/{self.username}/{self.password}/{stream_id}.{ext}"
+
+    def build_vod_stream_url(self, stream_id: str, ext: str = "mkv") -> str:
+        return f"{self.base_url}/movie/{self.username}/{self.password}/{stream_id}.{ext}"
+
+    def build_series_stream_url(self, stream_id: str, ext: str = "mkv") -> str:
+        return f"{self.base_url}/series/{self.username}/{self.password}/{stream_id}.{ext}"
+
+    def get_xmltv_url(self) -> str:
+        return f"{self.base_url}/xmltv.php?username={self.username}&password={self.password}"
+
+    async def test_connection(self) -> bool:
+        try:
+            info = await self.get_user_info()
+            return info.get("user_info", {}).get("status") == "Active"
+        except Exception as e:
+            logger.warning(f"Provider connection test failed: {e}")
+            return False