Electronics Catalog: API, MCP server, frontend and deployment

Verified catalogue of mobiles and laptops sold in India, collected from
real retail listings (FastAPI backend, React frontend, Postgres/pgvector).

- REST API under /api/elec (read-only catalogue; admin endpoints need login)
- MCP server (FastMCP) at /mcp/ with list_categories, search_products,
  get_product and price_history tools
- Real ratings and reviews read from product pages and search results
- Production Dockerfile (requirements-api.txt, no PyTorch) and
  .env.production.example; remote database only via an explicit
  ELEC_ALLOW_REMOTE_DB host/name allowlist
- docs/API.md: endpoint and MCP reference with live examples

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

backend/app/electronics/net/breaker.py

@@ -0,0 +1,61 @@
+"""Per-host circuit breaker.
+
+One 403, 429, 503 or CAPTCHA page opens the breaker for that host for
+ELEC_BREAKER_COOLDOWN_HOURS. While it is open the host is not requested at all
+and its products are collected from web search results instead. There is no
+retry-with-a-different-identity: a block is an answer.
+"""
+from __future__ import annotations
+
+import threading
+import time
+from typing import Callable, Dict, Optional, Tuple
+
+from app.infrastructure.settings import ELEC_BREAKER_COOLDOWN_HOURS
+
+
+class CircuitBreaker:
+    def __init__(
+        self,
+        cooldown_seconds: float = ELEC_BREAKER_COOLDOWN_HOURS * 3600,
+        on_trip: Optional[Callable[[str, str, float], None]] = None,
+        clock: Callable[[], float] = time.time,
+    ) -> None:
+        self.cooldown = cooldown_seconds
+        self.on_trip = on_trip
+        self._clock = clock
+        self._open: Dict[str, Tuple[float, str]] = {}
+        self._lock = threading.Lock()
+
+    @staticmethod
+    def _key(host: str) -> str:
+        host = host.lower()
+        return host[4:] if host.startswith("www.") else host
+
+    def preload(self, host: str, until_epoch: float, reason: str) -> None:
+        """Restore a breaker that was opened in an earlier run (elec.site)."""
+        if until_epoch > self._clock():
+            with self._lock:
+                self._open[self._key(host)] = (until_epoch, reason)
+
+    def trip(self, host: str, reason: str) -> None:
+        until = self._clock() + self.cooldown
+        with self._lock:
+            self._open[self._key(host)] = (until, reason)
+        if self.on_trip:
+            self.on_trip(self._key(host), reason, until)
+
+    def is_open(self, host: str) -> bool:
+        key = self._key(host)
+        with self._lock:
+            entry = self._open.get(key)
+            if not entry:
+                return False
+            if entry[0] <= self._clock():
+                del self._open[key]
+                return False
+            return True
+
+    def reason(self, host: str) -> Optional[str]:
+        entry = self._open.get(self._key(host))
+        return entry[1] if entry else None