Peering: admin console visibility for peers, feeds, spend and held invoices #939

Part of the relay peering work in #931.

Scope

Operator visibility for peering, alongside the existing mirror/worker panels in the admin operations console:

• Configured peers: pubkey, endpoint, terms, relationship state (active / suspended / lapsed).
• Feed health per peer: last sync/reconciliation, live-feed status, events served via feed vs on-demand requests.
• Money per peer per period: invoices received, paid, held; budget remaining; held invoices actionable (approve → pay manually, or reject).
• Budget-exhaustion and held-invoice events are visible without reading logs.

Follows the existing ops-console patterns for data access (bounded queries, same admin auth/rate-limit chain).

Acceptance

• An operator can answer "who are we peering with, what has it cost this period, and is anything waiting on me?" from the console alone.
• Approving a held invoice from the console pays it and activates the corresponding feed.