Sharpen pilot logging: ISO timestamps, level labels, transport-error classification, per-frame info

- Emit ISO-8601 timestamps and string level labels (info/warn/...) so
  Portainer's log viewer renders seconds and human-readable levels.
- Classify ETIMEDOUT/ECONNRESET/EPIPE/ENOTCONN as info one-liners
  rather than warns with stack traces. These are routine on cellular.
- Add an info "frame ingested" line per accepted AVL frame so device
  activity is visible at info level until task 1.10 wires up prom-client.

src/adapters/teltonika/index.ts

@@ -134,6 +134,19 @@ export function createTeltonikaAdapter(options: TeltonikaAdapterOptions): Adapte
                 'malformed frame; dropping connection',
               );
             }
+          } else if (
+            err instanceof Error &&
+            'code' in err &&
+            // Routine on cellular: NAT timeouts, carrier RST, half-closed pipes.
+            // Surface as info (one-liner, no stack) so warns mean something.
+            ['ETIMEDOUT', 'ECONNRESET', 'EPIPE', 'ENOTCONN'].includes(
+              (err as NodeJS.ErrnoException).code as string,
+            )
+          ) {
+            sessionLogger.info(
+              { code: (err as NodeJS.ErrnoException).code },
+              'session ended (transport error)',
+            );
           } else {
             sessionLogger.warn({ err }, 'unexpected error reading frame; dropping connection');
           }
@@ -204,6 +217,13 @@ export function createTeltonikaAdapter(options: TeltonikaAdapterOptions): Adapte
           result: 'ok',
         });
 
+        // Pilot-stage visibility into per-frame ingest. Downgrade to debug
+        // once task 1.10 wires up prom-client and frames_total is scrapeable.
+        sessionLogger.info(
+          { codec: codecLabel, records: result.recordCount },
+          'frame ingested',
+        );
+
         // ACK: 4-byte big-endian record count
         const ack = Buffer.alloc(4);
         ack.writeUInt32BE(result.recordCount, 0);

src/observability/logger.ts

@@ -22,10 +22,19 @@ export function createLogger(options: {
     instance_id: instanceId,
   };
 
+  // Emit `"level":"info"` instead of pino's default `"level":30` so log
+  // viewers (Portainer, etc.) show a human-readable label rather than the
+  // numeric level.
+  const formatters = {
+    level: (label: string) => ({ level: label }),
+  };
+
   if (nodeEnv === 'development') {
     return pino({
       level,
       base,
+      timestamp: pino.stdTimeFunctions.isoTime,
+      formatters,
       transport: {
         target: 'pino-pretty',
         options: {
@@ -37,6 +46,8 @@ export function createLogger(options: {
     });
   }
 
-  // Production and test: plain JSON — fast, no extra deps
-  return pino({ level, base });
+  // Production and test: plain JSON — fast, no extra deps.
+  // ISO-8601 string timestamps (vs default epoch-ms) survive downstream
+  // log renderers (Portainer, Docker --timestamps) without losing seconds.
+  return pino({ level, base, timestamp: pino.stdTimeFunctions.isoTime, formatters });
 }