Harden server logging and production boot experience

Replace ad-hoc console output with a structured logger (pretty/JSON,
levels, redaction, optional file rotation), a clean startup banner with
Docker/feature probes, graceful shutdown signals, and slow-RPC warnings.

docs/OPERATOR.md

@@ -67,6 +67,27 @@ Vault file: `peardock-vault.json` (mode 600). Override path with `PEARDOCK_VAULT
 | `PEARDOCK_UNRESTRICTED_CLI=1` | Broader `docker` CLI for **admin** |
 | `PEARDOCK_BROWSE_OPEN=1` | Legacy open host FS browse (discouraged) |
 
+## Logging
+
+| Env | Effect |
+|-----|--------|
+| `LOG_LEVEL` | `error` · `warn` · `info` (default in production) · `debug` (default in dev) |
+| `LOG_FORMAT` | `pretty` (TTY default) · `json` (default when non-TTY / good for journald) |
+| `ENABLE_FILE_LOGGING=1` | Append JSON lines under `LOG_DIR` (default `./logs`) with size rotation |
+| `LOG_DIR` | Directory for file logs |
+| `NO_COLOR=1` | Disable ANSI colors in pretty mode |
+| `LOG_STACK=1` | Include error stacks in structured fields |
+
+Examples:
+
+```bash
+# systemd / journald
+LOG_FORMAT=json LOG_LEVEL=info npm run server
+
+# local development
+LOG_LEVEL=debug npm run server
+```
+
 ## Compose stacks
 
 `deployStack` accepts: