fix: remove aggregator controller and share aggregator state wit…

[perfogic]

What was wrong?

Fixes #1430.

• POST /lean/v0/admin/aggregator updated NetworkState.is_aggregator, but the actual aggregation paths in LeanChainService used their own boot-time is_aggregator value.
  => This made the admin API misleading because toggling it did not affect chain-service aggregation behavior.

How was it fixed?

• Deleted AggregatorController and stopped routing the admin endpoint through a separate controller layer.
• Removed is_aggregator from NetworkState; network state should not own the aggregator role.
• Added AggregatorState as the shared runtime flag for the node's aggregator role.
• Passed that same state into both the RPC handlers and LeanChainService.
• Changed the chain service to read the shared flag when deciding whether to aggregate during ticks or gossip attestation handling.
• Left prover setup and subnet subscriptions as boot-time behavior for now.

To-Do

• I have read CONTRIBUTING.md.
• This PR title follows conventional commits.

[perfogic]

Illustration about how this PR works

• Before this PR, the admin API and the chain service used different aggregator role states (is_aggregator).

For Admin API:
  POST /lean/v0/admin/aggregator
          |
          v
  RPC aggregator handler
          |
          v
  AggregatorController.set_enabled(enabled)
          |
          v
  NetworkState.is_aggregator
          |
          v
  GET /lean/v0/admin/aggregator
 For Chain Service:
   config.is_aggregator
          |
          v
  LeanChainService.is_aggregator
          |
          +--> tick_interval(..., is_aggregator)
          |
          +--> on_gossip_attestation(..., is_aggregator)

=> This lead to the case that aggregator role was enabled while the chain service still behaved as a non-aggregator.

• After this PR, both RPC and chain-service aggregation checks share the same live role state, which is AggregatorState:

config.is_aggregator
        |
        v
AggregatorState
        |
        +------------------------------+
        |                              |
        v                              v
RPC admin aggregator handlers   LeanChainService
GET/POST /admin/aggregator      tick_interval(...)
                                on_gossip_attestation(...)