Container security hardening (phase 2) (#24068)

* Create frigate and go2rtc runtime users in the image

* Add single fix-ownership helper for volume permission migration

* Add init-usermod oneshot for PUID and PGID remapping

* Chown newly created runtime directories to the frigate user

* Run sentinel-guarded ownership sweep during prepare

* Add host-side volume permission migration script

* Guard log directory ownership for user-mode startup

* Fall back to plain s6-log when running without root

* Assert PUID remapping and sweep sentinel in CI smoke test

* Skip the ownership sweep in the devcontainer

* Pin FRIGATE_RUN_AS_ROOT in ownership tests

* Do not record the sweep as complete when a chown failed

* Validate PUID and PGID in the migration script

* Treat a failed ownership scan as an incomplete sweep

* Reject PUID and PGID of 0 during remapping

* Handle symlinks, dry runs, and sentinel write failures in the sweep

* Treat an absent sweep root as an incomplete sweep

docker/main/rootfs/etc/s6-overlay/s6-rc.d/prepare/run

@@ -144,3 +144,16 @@ rm -f /dev/shm/.frigate-is-stopping
 
 migrate_addon_config_dir
 migrate_db_from_media_to_config
+
+# Align volume ownership with the runtime user (one sweep per PUID/schema
+# change, guarded by the sentinel; see fix-ownership). The escape hatch
+# deletes the sentinel instead: ownership is never mutated while it is on,
+# so the next non-root boot must re-sweep whatever root created meanwhile.
+if [[ "$(id -u)" -eq 0 ]]; then
+    if [[ "${FRIGATE_RUN_AS_ROOT:-false}" == "true" ]]; then
+        rm -f /config/.permissions_version
+    else
+        /usr/local/bin/fix-ownership --sentinel /config/.permissions_version \
+            "${PUID:-1000}" "${PGID:-1000}" /config /media/frigate
+    fi
+fi