loki-app release v0.45.0

Upgrade upstream loki helm chart from v11 (11.6.4) to v13 (13.5.0). Loki app version unchanged at 3.7.1.
Pin loki.deploymentMode to SimpleScalable in values.yaml. Upstream v13 changed the default to Monolithic; this preserves the existing backend/read/write topology.
Move gateway route configuration from loki.gateway.route to top-level gatewayRoute. Upstream v13 redefined gateway.route as a strict-schema map of named routes that rejected our flat structure. Consumers overriding loki.gateway.route.* must rename to gatewayRoute.*.
- Note: It’s better if you use the upstream loki.gateway.route. The gatewayRoute section is here for compatibility, and keeping a few extra features we had added.

New default livenessProbe on every loki pod (/loki/api/v1/status/buildinfo, 30s period, 10× failure threshold ≈ 5 min before kill).
Memberlist hardening: defaults add abort_if_cluster_join_fails, IPv6-friendly advertise_addr: ${HASH_RING_INSTANCE_ADDR} (auto-injected from status.podIP), join retry/backoff. Backend/read/write pods now run with -config.expand-env=true.
Server tuning defaults added (graceful_shutdown_timeout: 5s, gRPC keepalive, grpc_server_max_concurrent_streams: 1000, 100 MiB gRPC msg size, http_server_idle_timeout: 30s).
k8s-sidecar bumped 2.6.0 → 2.7.1; gains /healthz liveness/readiness probes on new http-sidecar port (8080).
Gateway nginx image bumped 1.29-alpine → 1.30-alpine.