fix: address code review findings (C1, I1, I2)

- C1: Include 'unreachable' peers in queueOutboxEvent query to prevent
  UNIQUE constraint violation when creating placeholders
- I1: Add 'rejected' to StatusFilter in FederationPanel so admins can
  see and manage rejected peers with delete/re-initiate actions
- I2: Map ensurePeered 'failed' to 'pending' in peer/ensure response
  to match spec and client expectations

packages/server/src/utils/federationOutbox.ts

@@ -138,7 +138,7 @@ export function queueOutboxEvent(
       .select()
       .from(schema.federationPeers)
       .where(
-        inArray(schema.federationPeers.status, ['active', 'pending']),
+        inArray(schema.federationPeers.status, ['active', 'pending', 'unreachable']),
       )
       .all();