Dnsmasq/Hosts UI tweaks, test harness: down before redeploy, exclude leases from mount

- Dnsmasq page: Config (Main config, Managed file, Config set) under Service configuration; remove Paths/Leases (in Effective config DHCP); EffectiveConfigSection collapsible groups; StatusSection flex-wrap
- Hosts: HostsFileSection always shows table; 'No host entries' in tbody when empty
- Models: reorganize into sub-namespaces (Config, EffectiveConfig, Hosts, Dhcp, Status); move EffectiveConfig/Status/Logs components under Dnsmasq
- Test harness: prepare-test-mount.sh runs 'docker compose down' before mount+up so all containers (including DHCP clients) restart; exclude testdata/leases from sync (unit tests only); testdata/README

scripts/prepare-test-mount.sh

@@ -168,6 +168,10 @@ if [ ! -d "$SOURCE_DIR" ]; then
   exit 1
 fi
 
+# Take the harness down so all containers (including one-shot DHCP clients) are recreated on up.
+echo "Stopping test harness: docker compose -f $COMPOSE_FILE down"
+docker compose -f "$COMPOSE_FILE" down
+
 mkdir -p "$MOUNT_DIR"
 
 if [ "$NO_CLEAR" = false ]; then
@@ -176,9 +180,10 @@ if [ "$NO_CLEAR" = false ]; then
 fi
 
 if command -v rsync >/dev/null 2>&1; then
-  rsync -a "$SOURCE_DIR/" "$MOUNT_DIR/"
+  rsync -a --exclude='leases' "$SOURCE_DIR/" "$MOUNT_DIR/"
 else
   cp -r "$SOURCE_DIR/." "$MOUNT_DIR/"
+  rm -f "$MOUNT_DIR/leases"
 fi
 
 # Remove any leftover managed config from previous runs so dnsmasq starts clean (app will create zz-dnsmasq-webui.conf on startup).