feat: add GET /api/v1/nodes/{id} detail endpoint

[Nic-dorman]

Summary

Adds a detail endpoint for individual nodes, returning full config + runtime state.

The problem: The status endpoint (GET /api/v1/nodes/status) returns only summary info (id, name, version, status, pid, uptime). GUI clients need access to data_dir, rewards_address, ports, binary_path, etc. — currently only available by reading the node_registry.json file directly, which is fragile (path can be custom).

The fix: GET /api/v1/nodes/{id} returns the existing NodeInfo type — full NodeConfig (flattened via serde) plus runtime state from the supervisor.

Response example

{
  "id": 1,
  "service_name": "node1",
  "rewards_address": "0x1234...",
  "data_dir": "/home/user/.local/share/ant/nodes/node-1",
  "log_dir": null,
  "node_port": null,
  "metrics_port": null,
  "network_id": 1,
  "binary_path": "/home/user/.local/share/ant/nodes/node-1/saorsa-node",
  "version": "0.4.1",
  "env_variables": {},
  "bootstrap_peers": [],
  "status": "running",
  "pid": 12345,
  "uptime_secs": 3600
}

Changes

• server.rs: Added get_node_detail handler, routed as GET alongside existing DELETE on /api/v1/nodes/{id}
• daemon_integration.rs: E2e test — verifies full config response, flattened JSON shape, and 404

Tests

• All 5 daemon integration tests pass
• Clippy clean, fmt clean

Test plan

• cargo test -p ant-core --test daemon_integration — 5 pass
• cargo clippy -p ant-core -- -D warnings clean

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