MutationRow.op was str despite _MUTATION_OPS existing; Topology.mode/status,
TopologyDecky.state, TopologyMutation.op/state carried valid values only in
comments; deferred json import had no justification.
- Promote _MUTATION_OPS before table classes so table fields can reference it
- Add sa_column=Column(String) on each Literal-annotated table field to satisfy
SQLModel 0.0.38 column-type inference
- Move import json to module top; remove deferred import inside _decode_json_payload
- MutationRow.op: str -> _MUTATION_OPS
Adds a fleet_singletons array to ServiceCatalogResponse so per-decky
add UIs can filter out services like LLMNR that run once fleet-wide
(and would 422 server-side at the live add endpoint).
The existing 'services: list[str]' field is unchanged for back-compat
with MazeNET/useMazeApi.ts:257; the new field is additive.
decnet_web/src/hooks/useServiceRegistry.ts wraps the endpoint with a
module-scoped cache (registry only changes on BYOS install / plugin
drop, neither of which happens mid-session) and exposes a precomputed
.perDecky list so consumers don't need to re-derive the diff.
