Pin logging stack images; fix Loki common.instance_addr placement

:latest images (loki 3.7.3/go1.26.4, presumably grafana/alloy too) reset
every TCP connection on this host — kernel is 5.16.7 (Fedora 35, EOL
since 2023), too old for whatever the newer Go toolchains need.
Confirmed via a disposable grafana/loki:2.9.8 test container: same
config, same host, works cleanly. Pin all three images to older stable
releases instead of chasing this again on every redeploy.

Also fixes an unrelated config bug: instance_addr belongs directly
under `common:`, not nested under `common.ring:` — the misplaced field
was silently ignored, which didn't help but wasn't the actual cause.

logging/docker-compose.yaml

@@ -2,7 +2,10 @@ version: '3.8'
 
 services:
   loki:
-    image: grafana/loki:latest
+    # Pinned, not :latest — this host's kernel (5.16.7, Fedora 35 from 2022) resets
+    # every TCP connection to containers built with newer Go toolchains
+    # (confirmed: grafana/loki:latest, built with go1.26.4, fails; 2.9.8 works).
+    image: grafana/loki:2.9.8
     container_name: loki
     command: -config.file=/etc/loki/config.yaml
     restart: unless-stopped
@@ -13,7 +16,8 @@ services:
       - logging-nw
 
   alloy:
-    image: grafana/alloy:latest
+    # Pinned for the same reason as loki — see comment there.
+    image: grafana/alloy:v1.4.3
     container_name: alloy
     command:
       - run
@@ -35,7 +39,8 @@ services:
       - logging-nw
 
   grafana:
-    image: grafana/grafana:latest
+    # Pinned for the same reason as loki — see comment there.
+    image: grafana/grafana:10.4.2
     container_name: grafana
     restart: unless-stopped
     depends_on: