Add structured logging throughout the backend

Request-level logging middleware (method/path/status/duration),
per-module loggers in routes/services (nearby search radius
expansion, 404s, name search), LOG_LEVEL setting wired through
docker-compose, and seed_loader converted from print() to logging.

Verified: pytest passes, and manually confirmed log lines appear for
both successful and 404 requests via `docker compose logs api`.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/app/services/geocoding.py

@@ -4,6 +4,8 @@ Used when the user denies location permission and types a place of interest,
 or when 2GIS's own geocoding API isn't wired into a given client flow yet.
 """
 
+import logging
+
 from geoalchemy2 import Geometry
 from sqlalchemy import and_, cast, func, select
 from sqlalchemy.orm import Session
@@ -13,6 +15,8 @@ from app.models.enums import ContentLanguage, ContentLength
 from app.models.place import Place
 from app.models.place_content import PlaceContent
 
+logger = logging.getLogger("guidecity.geocoding")
+
 
 def search_places(
     db: Session,
@@ -44,4 +48,6 @@ def search_places(
     if city_slug is not None:
         stmt = stmt.join(City, City.id == Place.city_id).where(City.slug == city_slug)
 
-    return db.execute(stmt).all()
+    results = db.execute(stmt).all()
+    logger.info("name search q=%r city_slug=%s lang=%s -> %d result(s)", q, city_slug, language, len(results))
+    return results