fix: node graceful shutdown by handling SIGTERM (#2335)

## Fix graceful shutdown in Docker containers

### Problem
When running the rollkit node in a Docker container and using `docker
stop`, the process doesn't shutdown gracefully and causes database
corruption.

### Logs

```
7:00AM INF creating empty block height=10 module=BlockManager
7:00AM INF creating empty block height=11 module=BlockManager
7:00AM INF creating empty block height=12 module=BlockManager

# command: `docker stop <container_name>

# command: `docker start <container_name>

7:00AM INF creating new client module=main namespace=000000000000000000000000000000000000002777d4d961c75a526dd8
7:00AM INF using default mempool ttl MempoolTTL=25 module=BlockManager
7:00AM INF starting P2P client module=main
7:00AM INF started RPC server addr=127.0.0.1:7331 module=main
7:00AM INF listening on address=/ip4/127.0.0.1/tcp/7676/p2p/12D3KooWMubR4af4S9VW9xZMix4HYptuM9htnvccLuT6q7BhAGWf module=main
7:00AM INF listening on address=/ip4/172.28.0.4/tcp/7676/p2p/12D3KooWMubR4af4S9VW9xZMix4HYptuM9htnvccLuT6q7BhAGWf module=main
7:00AM INF no peers - only listening for connections module=main
7:00AM INF working in aggregator mode block time=1s module=main
7:00AM INF Reaper started interval=1000 module=Reaper
7:00AM INF creating empty block height=13 module=BlockManager
7:00AM ERR unrecoverable error in one of the go routines... error="error in normal aggregation loop: error while publishing block: failed to broadcast: validation failed" module=main
7:00AM INF halting full node and its sub services... module=main
7:00AM INF data submission loop stopped module=BlockManager
7:00AM INF Reaper stopped module=Reaper
2025-06-04T07:00:46.080Z	ERROR	header/sync	sync/sync.go:229	syncing headers	{"from": 2, "to": 13, "err": "header/p2p: exchange is closed"}
7:00AM INF full node halted successfully module=main
7:00AM ERR node error error="context canceled" module=main
Error: context canceled
```


### Solution
- Added `SIGTERM` signal handling alongside existing `SIGINT` handling
- Added `syscall` import to support `syscall.SIGTERM`
- Now responds to both interactive shutdown (Ctrl+C) and Docker stop
commands

### Changes
- Modified `StartNode()` function in `cmd/run_node.go` to listen for
both `os.Interrupt` and `syscall.SIGTERM`
- Added `syscall` import

### Testing
- [x] Graceful shutdown with Ctrl+C still works
- [x] Graceful shutdown with `docker stop` now works
- [x] No database corruption after Docker container shutdown

```
7:00AM INF creating empty block height=10 module=BlockManager
7:00AM INF creating empty block height=11 module=BlockManager
7:00AM INF creating empty block height=12 module=BlockManager

# command: `docker stop <container_name>

7:04AM INF shutting down node... module=main
7:04AM INF context canceled, stopping node module=main
7:04AM INF halting full node and its sub services... module=main
7:04AM INF Reaper stopped module=Reaper
7:04AM INF data submission loop stopped module=BlockManager
7:04AM INF full node halted successfully module=main

# command: `docker start <container_name>

7:04AM INF creating new client module=main namespace=000000000000000000000000000000000000002777d4d961c75a526dd8
7:04AM INF using default mempool ttl MempoolTTL=25 module=BlockManager
7:04AM INF starting P2P client module=main
7:04AM INF started RPC server addr=127.0.0.1:7331 module=main
7:04AM INF listening on address=/ip4/127.0.0.1/tcp/7676/p2p/12D3KooWS5qA2Soarjzy5CwVukArsqnZ9qyAq1wWxoCyZ9q3egKv module=main
7:04AM INF listening on address=/ip4/172.28.0.4/tcp/7676/p2p/12D3KooWS5qA2Soarjzy5CwVukArsqnZ9qyAq1wWxoCyZ9q3egKv module=main
7:04AM INF no peers - only listening for connections module=main
7:04AM INF working in aggregator mode block time=1s module=main
7:04AM INF Reaper started interval=1000 module=Reaper
7:04AM INF creating empty block height=13 module=BlockManager
7:04AM INF creating empty block height=14 module=BlockManager

```


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **New Features**
- The application now supports graceful shutdown when receiving SIGTERM
signals, in addition to existing support for SIGINT.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: auricom

pkg/cmd/run_node.go

@@ -8,6 +8,7 @@ import (
 	"os/signal"
 	"path/filepath"
 	"strings"
+	"syscall"
 	"time"
 
 	"cosmossdk.io/log"
@@ -168,7 +169,7 @@ func StartNode(
 
 	// Wait for interrupt signal to gracefully shut down the server
 	quit := make(chan os.Signal, 1)
-	signal.Notify(quit, os.Interrupt)
+	signal.Notify(quit, os.Interrupt, syscall.SIGTERM)
 
 	select {
 	case <-quit: