Timers: built-in LTC listener, configured in the admin page

The LTC listener now lives inside the module: it spawns the native
ltc-capture helper (moved into the module folder, compiled on first use,
exact-name device matching) for the admin-selected input device, extracts
the configured channel, and decodes SMPTE LTC in-process (ltc.js — the
engine, shared with tools/ltc-reader.js, which remains the remote-machine
option posting to /ltc).

Admin config: an "LTC listener" switch, an audio-device select populated
live from the new GET /ltc/devices route, and a 1-based channel number.
The switch off means LTC is gone entirely: no LTC entry in the Add-tile
picker, no LTC row in the Timers menu or All-timers grid, no stage/API
probes, and POST /ltc answers 409. Source precedence with it on:
listener-with-data, fresh remote reader, listener's own no-signal verdict,
then the legacy API/stage chain.

Shell (admin page): `select` fields learn `optionsRoute` — options fetched
from a module route at render, saved value kept selectable when the route
or device is gone. Documented in MODULE-GUIDE; backward compatible.
Coordinate with the shell lane before its next admin.js change.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.gitignore

@@ -7,3 +7,6 @@ dist/
 # runtime state written by the admin page / layout saves
 config/modules.json
 config/layouts/
+
+# compiled per-machine, source sits next to it
+modules/propresenter-timers/ltc-capture