Implement `app/app.go` equivalent — node graph wiring & lifecycle

[varex83]

Scope

Port charon/app/app.go (~1256 LOC) — the integration anchor that instantiates every duty-pipeline component in the correct order with lifecycle hooks. This is the final assembly step that makes Pluto a runnable node.

Dependencies (must land first)

This issue cannot start until every component below is implemented:

Track A:

• Rewrite core/qbft to async-Rust-friendly API #393 core/qbft async
• core/consensus framework (controller/wrapper/debugger) — see Track A epic for issue number
• Implement core/consensus/qbft #157 core/consensus/qbft, Implement core/consensus/timer #158 timer, Implement core/consensus/instance #48 instance, Implement core/consensus/metrics #62 metrics, Implement core/consensus/mocks #39 mocks
• Implement core/scheduler #176 core/scheduler, Implement core/dutydb #171 core/dutydb, Implement core/fetcher #172 core/fetcher, Implement core/bcast #170 core/bcast

Track B:

• Implement core/validatorapi #180 core/validatorapi, Implement core/tracker #179 core/tracker, Implement core/sigagg #178 core/sigagg, Implement core/aggsigdb #169 core/aggsigdb

Track C:

• Implement app/health #68 app/health, Implement app/sse #183 app/sse, app/monitoringapi
• core/gater, Implement core/priority #177 core/priority, Implement core/infosync #173 core/infosync

Acceptance

• All components instantiated with proper lifecycle ordering (start/stop semantics match Go)
• Channel/event wiring matches the Go graph
• Unit-level integration test boots the graph against beaconmock (Implement testutil/beaconmock #37)
• cargo clippy --workspace --all-targets --all-features -- -D warnings clean