feat: implement pass_mgr, pcexec, and safe-restart modules

- Add pass_mgr Go binary with AES-256-GCM encryption
- Add pcexec TypeScript tool with password sanitization
- Add safe-restart module with state machine and API
- Add slash command handler with cooldown support
- Update README with usage documentation

pass_mgr/go.mod

@@ -0,0 +1,12 @@
+module pass_mgr
+
+go 1.22
+
+require (
+	github.com/spf13/cobra v1.8.0
+)
+
+require (
+	github.com/inconshreveable/mousetrap v1.1.0 // indirect
+	github.com/spf13/pflag v1.0.5 // indirect
+)