feat: log the plaintext RAM APDUs of the install steps (v3.6.19)

`_ram_send_gp_apdu` (the shared step sender of /api/ram-install and
/api/ram-install-app) now logs every step's plaintext APDU and packed
packet, like /api/send-ota's unconditional lines:

  RAM C-APDU (INSTALL [for load]): 80E602000C07F0414C4641610100000000
  RAM SECURED-PACKET (INSTALL [for load]): 00281516212525000000...

No flag - the step name keeps the sequence readable, and --apdu-trace stays
the card-level (ENVELOPE) trace.  Tests: the logging pinned with stubbed
packet builders.

498 Python / 650 frontend green; version 3.6.19; sw simple-v292.

frontend/index.html

@@ -1711,7 +1711,7 @@
 // ===== Version =====
 // Single source of truth for the PWA version: shown in the header and used
 // by the server version check in pysimConnect().
-const SIMPLE_VERSION = '3.6.18';
+const SIMPLE_VERSION = '3.6.19';
 document.getElementById('app-version').textContent = 'v' + SIMPLE_VERSION;
 
 // ===== Tab switching =====