Add background-hash-mark addition for region routing

Per https://buymeacoffee.com/ripplebiz/region-filtering:

> After some discussions, and that there is some confusion
around #channels and #regions, it's been decided to drop
the requirement to have the '#' prefix. So, region names
will just be plain alphanumeric (and '-'), with no # prefix.

> For backwards compatibility, the names will internally have
a '#' prepended, but for all client GUI's and command lines,
you generally won't see mention of '#' prefixes. The next
firmware release (v1.12.0) and subsequent Ripple firmware
and Liam's app will have modified UI to remove the '#' requirement.

So, silently add, but don't duplicate, for users who have already
added hashmarks.

app/radio.py

@@ -262,10 +262,11 @@ class RadioManager:
 
                     # Apply flood scope from settings (best-effort; older firmware
                     # may not support set_flood_scope)
+                    from app.region_scope import normalize_region_scope
                     from app.repository import AppSettingsRepository
 
                     app_settings = await AppSettingsRepository.get()
-                    scope = app_settings.flood_scope
+                    scope = normalize_region_scope(app_settings.flood_scope)
                     try:
                         await mc.commands.set_flood_scope(scope if scope else "")
                         logger.info("Applied flood_scope=%r", scope or "(disabled)")