scp81: rename passthru to redirect, add a true passthru mode (v2.2.13)

The former 'passthru' mode is now 'redirect': it pins the configured target
and every BIP channel is connected there (the card's requested address is
only logged; host/port required). The name 'passthru' now means the new mode:
no listener and no target - each channel dials the destination the card
requests in OPEN CHANNEL (Other address + Transport level port, TCP client,
remote, 0x02 only). The specs define no default port (TS 102 223 8.59), so an
incomplete or non-TCP request fails the channel with result 3A and an
open-fail log reason.

BipTerminal gains a mode (enable(host, port, mode=...), open(..., proto=...)),
reports it in status(), and the control API/status expose redirect (target)
and passthru (per-channel targets). The PWA mode selector shows four modes
with per-mode notes and disables Host/Port in passthru; the status line shows
each channel's actual target. Docs, help (EN/RU), READMEs and the AGENTS notes
updated; SW cache otaman-v179.

Breaking API change: mode:'passthru' has the new semantics - use
mode:'redirect' for the previous behavior (no alias).

frontend/sw.js

@@ -1,4 +1,4 @@
-const CACHE = 'otaman-v178';
+const CACHE = 'otaman-v179';
 const URLS = [
   'index.html',
   'help.html',