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/db/connection.py

@@ -0,0 +1,68 @@
+"""Connections to the local electronics database.
+
+settings.py has already refused to load unless DB_HOST is local and DB_NAME is
+electronics_catalog, so nothing here can reach another database.
+"""
+from __future__ import annotations
+
+import logging
+from contextlib import contextmanager
+from typing import Iterator
+
+import psycopg
+from psycopg.rows import dict_row
+
+from app.infrastructure.settings import (
+    DB_CONNECT_TIMEOUT_SECONDS,
+    DB_HOST,
+    DB_NAME,
+    DB_PASSWORD,
+    DB_PORT,
+    DB_USER,
+)
+
+logger = logging.getLogger(__name__)
+
+
+def connect(*, autocommit: bool = False) -> psycopg.Connection:
+    conn = psycopg.connect(
+        host=DB_HOST,
+        port=DB_PORT,
+        dbname=DB_NAME,
+        user=DB_USER,
+        password=DB_PASSWORD,
+        connect_timeout=DB_CONNECT_TIMEOUT_SECONDS,
+        autocommit=autocommit,
+        row_factory=dict_row,
+    )
+    try:
+        from pgvector.psycopg import register_vector
+
+        register_vector(conn)
+    except Exception:  # noqa: BLE001 - the extension is created by migration 0001
+        pass
+    return conn
+
+
+@contextmanager
+def transaction() -> Iterator[psycopg.Connection]:
+    """A connection whose work is committed on success, rolled back on error."""
+    conn = connect()
+    try:
+        yield conn
+        conn.commit()
+    except Exception:
+        conn.rollback()
+        raise
+    finally:
+        conn.close()
+
+
+def check_connection() -> bool:
+    try:
+        with connect(autocommit=True) as conn:
+            conn.execute("SELECT 1")
+        return True
+    except Exception as exc:  # noqa: BLE001 - a health probe reports, never raises
+        logger.debug("Database unreachable: %s", exc)
+        return False