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/seed/seed_loader.py

@@ -6,26 +6,33 @@ Usage:
 """
 
 import argparse
+import logging
 from pathlib import Path
 
 import yaml
 
+from app.core.logging import configure_logging
 from app.db.session import SessionLocal
 from app.models.city import City
 from app.models.place import Place
 from app.models.place_content import PlaceContent
 
+logger = logging.getLogger("guidecity.seed_loader")
+
 
 def load_cities(path: Path) -> None:
+    logger.info("loading cities from %s", path)
     data = yaml.safe_load(path.read_text(encoding="utf-8"))
     db = SessionLocal()
     try:
         for c in data["cities"]:
             city = db.query(City).filter(City.slug == c["slug"]).one_or_none()
             if city is None:
+                logger.debug("creating new city slug=%r", c["slug"])
                 city = City(slug=c["slug"], name_ru=c["name_ru"], name_en=c["name_en"])
                 db.add(city)
             else:
+                logger.debug("updating existing city slug=%r", c["slug"])
                 city.name_ru = c["name_ru"]
                 city.name_en = c["name_en"]
             center = c.get("center")
@@ -33,7 +40,10 @@ def load_cities(path: Path) -> None:
                 city.center_point = f"SRID=4326;POINT({center['lon']} {center['lat']})"
             db.flush()
         db.commit()
-        print(f"Loaded {len(data['cities'])} cities from {path.name}")
+        logger.info("loaded %d cities from %s", len(data["cities"]), path.name)
+    except Exception:
+        logger.exception("failed loading cities from %s", path)
+        raise
     finally:
         db.close()
 
@@ -79,6 +89,7 @@ def _upsert_content(db, place_id: int, language: str, length: str, title: str, b
 
 
 def load_places(path: Path) -> None:
+    logger.info("loading places from %s", path)
     data = yaml.safe_load(path.read_text(encoding="utf-8"))
     city_slug = data["city"]
 
@@ -86,11 +97,13 @@ def load_places(path: Path) -> None:
     try:
         city = db.query(City).filter(City.slug == city_slug).one_or_none()
         if city is None:
+            logger.error("city %r not found; run --cities seed/cities.yaml first", city_slug)
             raise SystemExit(
                 f"City '{city_slug}' not found. Run `--cities seed/cities.yaml` first."
             )
 
         for place_data in data["places"]:
+            logger.debug("upserting place slug=%r", place_data["slug"])
             place = _upsert_place(db, city.id, place_data)
             titles = place_data.get("title", {})
             for language, lengths in place_data["content"].items():
@@ -99,12 +112,16 @@ def load_places(path: Path) -> None:
                     _upsert_content(db, place.id, language, length, title, body.strip())
 
         db.commit()
-        print(f"Loaded {len(data['places'])} places from {path.name}")
+        logger.info("loaded %d places from %s", len(data["places"]), path.name)
+    except Exception:
+        logger.exception("failed loading places from %s", path)
+        raise
     finally:
         db.close()
 
 
 def main() -> None:
+    configure_logging()
     parser = argparse.ArgumentParser(description=__doc__)
     group = parser.add_mutually_exclusive_group(required=True)
     group.add_argument("--cities", help="Path to a cities YAML file")