feat(scopes): import cached regional MeshMapper catalogues

[n30nex]

Adds opt-in MeshMapper regional scope discovery while preserving manual keys and metadata. Validated catalogues, ETags and retry timing persist through restarts; failed refreshes retain the last good snapshot. Work runs outside ingestion, source candidates are IATA-limited, short-code collisions remain unresolved, and catalogue membership creates no traffic or forwarding evidence. The default is off; channel scope delivery is separate PR #176.

Closes #173. Follows server #172. Parent 0fc1398eecaa24f1dbdd0fae28bc259f15a439f2, head 235e2e0fd672febf8e236d5b5859ef3d660028df. Focused diff.

Validated after integration with accepted #177–#180: local build/format/vet/tests and published-head CI pass. The composed Pi build 2ed2e031 includes all current server candidates and independent #166; its full PostgreSQL suite passes, including route-lock batching/cancellation and queue behavior. An isolated 504-scope replay preserved 100 packets, 800 observations, 100 decrypted messages and 2,400 opt-in live hearings from 3,200 inputs while a later maintenance batch was blocked. This is fixture evidence, not a universal delivery guarantee.

The backend is deployed on the Pi preview with exact source and changelog, retaining configuration, schema042 and rollback. All earlier review features remain included. Owners retain merges and production release. AI-assisted implementation continues under the contributor’s standing project authorization.

[n30nex]

@MrAlders0n / Claude: #174 is ready for review at 71e4e871. It follows #172; the focused diff contains the optional cached importer, manual-ownership protection and regional/ambiguous matching safeguards.

The Pi composition eb99f752 has all existing candidates and imports seven YOW names. Actual incoming #yow adverts and scope filtering are verified. Native PostgreSQL, Linux race and exact-head CI/security checks pass; the original database/configuration/binary and an off-Pi private dump are retained. The changelog/source and shared roadmap are updated. Channel message tags are the next separate slice. No upstream merge or production switch was performed.