M6-T05: add Tibber GraphQL client + price refresh service + schedule

- app/integrations/tibber/client.py: fetch_price_range/fetch_current_price
  (priceInfoRange QUARTER_HOURLY, startsAt->UTC, no fixed node count assumption),
  TibberError/TibberAuthError; token never logged or put in exception text.
- app/services/tibber_prices.py: refresh_prices upserts by starts_at (idempotent),
  no-op unless an active kind=tibber contract + token exist.
- main.py: hourly tibber-refresh job (existing jobs/MQTT untouched). Tests added.

app/main.py

@@ -31,6 +31,7 @@ from app.services.config_page import build_runtime_settings, seed_missing_config
 from app.services.public_ip import check_public_ipv4_and_notify
 from app.services.modbus_poll import poll_all_enabled_devices, BASE_POLL_TICK_SECONDS
 from app.services.ha_discovery import publish_discovery, publish_states
+from app.services.tibber_prices import refresh_prices
 from scripts.app_db_adopt import AppDatabaseAdoptionError, validate_app_runtime_db
 
 logger = logging.getLogger(__name__)
@@ -63,6 +64,33 @@ def _run_scheduled_modbus_poll() -> None:
         session.close()
 
 
+def _run_scheduled_tibber_refresh() -> None:
+    """Scheduled job: fetch Tibber 15-minute prices and upsert into tibber_price.
+
+    Runs every hour so that:
+    - Today's prices are available from startup.
+    - Tomorrow's prices (published by Tibber around 13:00 CET / 11:00 UTC) are
+      picked up within an hour of publication without requiring a server restart.
+
+    The job is a no-op when:
+    - No active energy contract with kind="tibber" exists.
+    - The Tibber API token is empty in the runtime settings.
+
+    Any client exceptions (auth failures, network errors) are caught and logged
+    so that a single failed fetch does not crash the scheduler or affect the
+    other background jobs.
+    """
+    session_local = get_session_local()
+    session: Session = session_local()
+    try:
+        runtime_settings = build_runtime_settings(session, get_settings())
+        refresh_prices(session, runtime_settings)
+    except Exception:
+        logger.exception("_run_scheduled_tibber_refresh: unexpected error")
+    finally:
+        session.close()
+
+
 def _run_scheduled_ha_state_publish() -> None:
     """Periodic job: publish discovery configs + state + availability for all enabled exposed entities.
 
@@ -148,6 +176,17 @@ async def lifespan(_: FastAPI):
         max_instances=1,
         coalesce=True,
     )
+    # Tibber price refresh: fetch today + tomorrow every hour.
+    # The job is a no-op when no active tibber contract or token is configured,
+    # so it is safe to register unconditionally.
+    scheduler.add_job(
+        _run_scheduled_tibber_refresh,
+        trigger=IntervalTrigger(hours=1),
+        id="tibber-refresh",
+        replace_existing=True,
+        max_instances=1,
+        coalesce=True,
+    )
     scheduler.start()
 
     # MQTT: connect using DB-merged runtime settings so broker configured via UI