Add Snacks app: automated video library encoder with hardware acceleration

- Apps/snacks/: docker-compose.yaml (2.3.1, host networking, privileged, /dev/dri)
  and README.md with full security exception documentation for:
  network_mode:host, privileged:true, device mount /dev/dri
- apps.md: converted to agent-readable table backlog with instructions for future apps
- Jellyfin-ffmpeg paths as defaults, 1G memory reservation, amd64 only (single-arch image)
- Validation: ./scripts/validate-appstore.sh passes

Apps/docker-ip-addr-manager/backend/app/models.py

@@ -46,6 +46,8 @@ class EntryView:
     used: bool
     containers: list[str]
     usage_known: bool
+    dns_desired: bool = False
+    dns_last_error: str | None = None
 
     def to_dict(self) -> dict:
         return {
@@ -59,4 +61,6 @@ class EntryView:
             "used": self.used,
             "containers": self.containers,
             "usage_known": self.usage_known,
+            "dns_desired": self.dns_desired,
+            "dns_last_error": self.dns_last_error,
         }