feat(services): volume mounts + admin volume inventory (C1)

services.volumes JSONB [{type: volume|bind, source, target, read_only}]
mapped into every replica's container config at deploy and reconcile
time, hashed into the runtime spec so mount changes trigger
reconciliation. Mounted via existing docker.HostConfig.Mounts.

- RuntimeSpec.Volumes + specHash + mount.Mount mapping in createReplica
- Create/update service accepts volumes; PUT replaces the whole list
- Replica-count reconcile now goes through the deploy queue — the last
  raw `go` reconcile left that could race a build
- GET /admin/volumes inventories node volumes with in_use flags;
  DELETE /admin/volumes/:name removes unused ones (409 on in-use)
- CLI: services update --volume/--bind/--clear-volumes, volumes
  list|delete; MCP: services_update + volumes_list/delete
- Settings UI: Volumes section with mount editor
- Migration normalizes the nullable baseline column to NOT NULL [].

Verified live: deploy applies mounts to the container, docker
auto-creates named volumes, in-use deletion is refused.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/backend/migrations_goose/20261009000000_service_volumes.sql

@@ -0,0 +1,13 @@
+-- +goose Up
+-- Volume mounts on services: [{type: "volume"|"bind", source, target,
+-- read_only}]. Applied to every replica's container config at deploy and
+-- reconcile time. The baseline schema declared the column nullable with
+-- no default — this normalizes it.
+ALTER TABLE services ADD COLUMN IF NOT EXISTS volumes JSONB DEFAULT '[]'::jsonb;
+UPDATE services SET volumes = '[]'::jsonb WHERE volumes IS NULL;
+ALTER TABLE services ALTER COLUMN volumes SET DEFAULT '[]'::jsonb;
+ALTER TABLE services ALTER COLUMN volumes SET NOT NULL;
+
+-- +goose Down
+ALTER TABLE services ALTER COLUMN volumes DROP NOT NULL;
+ALTER TABLE services ALTER COLUMN volumes DROP DEFAULT;