Add custom service log file support with L key

- Add ServiceLogConfig structure for per-host service log paths
- Implement L key handler for custom log file viewing via tmux popup
- Update dashboard config to support service_logs HashMap
- Add tail -f command execution over SSH for real-time log streaming
- Update status line to show L: Custom shortcut
- Document configuration format in CLAUDE.md

Each service can now have custom log file paths configured per host,
accessible via L key with same tmux popup interface as journalctl.

Cargo.lock

@@ -270,7 +270,7 @@ checksum = "a1d728cc89cf3aee9ff92b05e62b19ee65a02b5702cff7d5a377e32c6ae29d8d"
 
 [[package]]
 name = "cm-dashboard"
-version = "0.1.48"
+version = "0.1.49"
 dependencies = [
  "anyhow",
  "chrono",
@@ -291,7 +291,7 @@ dependencies = [
 
 [[package]]
 name = "cm-dashboard-agent"
-version = "0.1.48"
+version = "0.1.49"
 dependencies = [
  "anyhow",
  "async-trait",
@@ -314,7 +314,7 @@ dependencies = [
 
 [[package]]
 name = "cm-dashboard-shared"
-version = "0.1.48"
+version = "0.1.49"
 dependencies = [
  "chrono",
  "serde",