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.

frontend/src/components/ChatHeader.tsx

@@ -2,6 +2,7 @@ import { useEffect, useState } from 'react';
 import { toast } from './ui/sonner';
 import { isFavorite } from '../utils/favorites';
 import { handleKeyboardActivate } from '../utils/a11y';
+import { stripRegionScopePrefix } from '../utils/regionScope';
 import { ContactAvatar } from './ContactAvatar';
 import { ContactStatusInfo } from './ContactStatusInfo';
 import type { Channel, Contact, Conversation, Favorite, RadioConfig } from '../types';
@@ -54,8 +55,8 @@ export function ChatHeader({
   const handleEditFloodScopeOverride = () => {
     if (conversation.type !== 'channel' || !onSetChannelFloodScopeOverride) return;
     const nextValue = window.prompt(
-      'Enter regional override flood scope for this room. This temporarily changes the radio flood scope before send and restores it after, which significantly slows room sends. Leave blank to clear.\n\nNote: some radio clients (including the official ones) implicitly add a "#" character to the beginning of a region specifier. That needs to be manually added here, so if you use the official app with region "Anytown", you should enter it here as "#Anytown".',
-      activeChannel?.flood_scope_override ?? ''
+      'Enter regional override flood scope for this room. This temporarily changes the radio flood scope before send and restores it after, which significantly slows room sends. Leave blank to clear.',
+      stripRegionScopePrefix(activeChannel?.flood_scope_override)
     );
     if (nextValue === null) return;
     onSetChannelFloodScopeOverride(conversation.id, nextValue);
@@ -140,7 +141,7 @@ export function ChatHeader({
         )}
         {conversation.type === 'channel' && activeChannel?.flood_scope_override && (
           <span className="basis-full sm:basis-auto text-[11px] text-amber-700 dark:text-amber-300 truncate">
-            Regional override active: {activeChannel.flood_scope_override}
+            Regional override active: {stripRegionScopePrefix(activeChannel.flood_scope_override)}
           </span>
         )}
         {conversation.type === 'contact' &&

frontend/src/components/settings/SettingsRadioSection.tsx

@@ -5,6 +5,7 @@ import { Button } from '../ui/button';
 import { Separator } from '../ui/separator';
 import { toast } from '../ui/sonner';
 import { RADIO_PRESETS } from '../../utils/radioPresets';
+import { stripRegionScopePrefix } from '../../utils/regionScope';
 import type {
   AppSettings,
   AppSettingsUpdate,
@@ -83,7 +84,7 @@ export function SettingsRadioSection({
 
   useEffect(() => {
     setAdvertIntervalHours(String(Math.round(appSettings.advert_interval / 3600)));
-    setFloodScope(appSettings.flood_scope);
+    setFloodScope(stripRegionScopePrefix(appSettings.flood_scope));
     setMaxRadioContacts(String(appSettings.max_radio_contacts));
   }, [appSettings]);
 
@@ -256,7 +257,7 @@ export function SettingsRadioSection({
       if (newAdvertInterval !== appSettings.advert_interval) {
         update.advert_interval = newAdvertInterval;
       }
-      if (floodScope !== appSettings.flood_scope) {
+      if (floodScope !== stripRegionScopePrefix(appSettings.flood_scope)) {
         update.flood_scope = floodScope;
       }
       const newMaxRadioContacts = parseInt(maxRadioContacts, 10);
@@ -554,10 +555,10 @@ export function SettingsRadioSection({
           id="flood-scope"
           value={floodScope}
           onChange={(e) => setFloodScope(e.target.value)}
-          placeholder="#MyRegion"
+          placeholder="MyRegion"
         />
         <p className="text-xs text-muted-foreground">
-          Tag outgoing flood messages with a region name (e.g. #MyRegion). Repeaters configured for
+          Tag outgoing flood messages with a region name (e.g. MyRegion). Repeaters configured for
           that region can forward the traffic, while repeaters configured to deny other regions may
           drop it. Leave empty to disable.
         </p>