Stake page: plain validators + labeled ancestor fallback #519

Part of #$E.

What to build: Staking shows what's actually there instead of resolving a target magically. The stake page lists the node's own validators (default first); when it has none, it lists the nearest ancestor's validators labeled "via {ancestor name}" ("Stake via Malaysia") — plain composition in the route from the validators-by-node read plus the parent chain the place page already loads. No resolver module, no sourceNodeId bookkeeping. The resolution machinery is deleted outright: resolveForStaking, stakeableNodeIds, and their recursive CTEs. stakeable on community listings simplifies to "this node has validators". The wallet staking transaction flow is unchanged. Behavior change (intended): descendant search dies — stake at a country no longer surfaces a city's validator from its subtree.

Blocked by: #$N3.

Acceptance criteria

• Node with validators: stake page shows them, default pre-selected (as today)
• Node without validators: nearest ancestor's validators shown, labeled "via {ancestor name}" (e.g. KL page shows Malaysia's pool)
• No validators anywhere in the chain: existing browse-children state
• Community listings: stakeable = has validators; resolver routes and recursive SQL are gone
• Staking transaction flow unchanged (same account IDs, same whitelist checks)
• pnpm run typecheck, pnpm run test, pnpm run lint pass