Suppress signal handlers for the whole init (LXMF.LXMRouter too)

v1.0.2 only neutralised signal.signal around RNS.Reticulum(), but
LXMF.LXMRouter.__init__ also calls signal.signal(SIGINT/SIGTERM) (LXMRouter.py
308-309), so init still crashed with "signal only works in main thread of the
main interpreter" when the router was constructed in the executor thread.

Wrap the entire _start init (both constructors) with signal.signal neutralised
instead of just the RNS constructor. Confirmed via upstream source that the
only relevant signal registration sites are RNS/Reticulum.py:366-367 and
LXMF/LXMRouter.py:308-309, both module-attribute calls, so the module-level
patch intercepts both.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

custom_components/reticulum/manifest.json

@@ -12,5 +12,5 @@
   "loggers": ["RNS", "LXMF"],
   "requirements": ["rns>=0.9.0", "lxmf>=0.6.0"],
   "single_config_entry": true,
-  "version": "1.0.2"
+  "version": "1.0.3"
 }