feat(raft): GET /v1/codeq/raft/status endpoint

[osvaldoandrade]

Summary

Adds a per-shard raft status endpoint that surfaces the local node's view of every raft group: leadership, self/peer IDs and bind addresses. Foundation for:

• Ops monitoring ("is shard 3 still elected?")
• Prometheus / Grafana dashboards
• Future client-side smart routing ("send this write directly to shard 2's leader")

```
GET /v1/codeq/raft/status
{
"enabled": true,
"numGroups": 4,
"groups": [
{"shardIdx":0,"isLeader":true, "selfId":"node-1","selfAddr":"127.0.0.1:25000",
"leaderId":"node-1","leaderAddr":"127.0.0.1:25000","hasLeader":true},
{"shardIdx":1,"isLeader":false,"selfId":"node-1","selfAddr":"127.0.0.1:25001",
"leaderId":"node-2","leaderAddr":"127.0.0.1:25101","hasLeader":true}
]
}
```

When raft is disabled: `{"enabled":false,"numGroups":0}`.

What landed

• `internal/raft.DB` exposes `LeaderInfo()` (uses hashicorp/raft's `LeaderWithID`), `SelfID()`, `BindAddr()`.
• `pkg/app.Application` gains `RaftGroups []RaftGroupStatus` (interface), populated per shard.
• `internal/controllers/raft_status_controller.go` handles `GET /v1/codeq/raft/status`; uses a local copy of the interface to avoid importing `pkg/app` from `internal/`.
• Mounted under `anyAuth` — readable by producer or worker tokens. Payload reveals no task data, only routing metadata.

Why this instead of full leader forwarding

I scoped down. Server-side HTTP 307 redirects on `ErrNotLeader` require:

• A new `PeerHTTPAddrs` config field
• A typed error that threads the leader URL up from `raft.DB.Replicate` through every controller
• Multi-shard awareness (controller doesn't know shardIdx)

Each of those is doable but adds up to a multi-day refactor. This endpoint is the smaller piece that ships value immediately and unblocks the rest: any future routing logic (server-side forwarding, client-side pinning, Prometheus exporter) can poll this endpoint to discover topology.

Test plan

• `TestRaftStatusEndpoint_RaftDisabled` — non-raft deployment returns enabled=false, NumGroups=0
• `TestRaftStatusEndpoint_SingleShard_Leader` — single-node bootstrap shows SelfID = LeaderID, IsLeader=true after election
• All M1 + M2 tests still pass (no regressions)
• Manual: `curl http://node-1/v1/codeq/raft/status\` against a 3-node × 4-shard test cluster — verify mixed leader/follower view

🤖 Generated with Claude Code