feat(companion): shared named-scope list, per-channel/repeater popup pickers

Replace the single device-wide Scope text field with a small named list
(wildcard "*" fixed first, plus a movable default): each channel picks one
scope of its own (matching the app's per-channel region picker, surfaced in
the channel-history title), and the repeater's Extra scopes multi-selects
from the same list instead of comma-typed names. Both pickers are popups
(PopupMenu gains addCheckItem()/a fillable-square checkbox glyph) over the
existing screen rather than a full-screen takeover.

Also fixes a stray-bits bug where a pre-existing prefs file's own sentinel
tail could read into the new repeat_extra_scope_mask/ch_scope_idx fields and
silently reappear as a real pick later once the scope list grew into that
range.

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

examples/companion_radio/DataStore.h

@@ -4,6 +4,7 @@
 #include <helpers/ContactInfo.h>
 #include <helpers/ChannelDetails.h>
 #include "NodePrefs.h"
+#include "ScopeList.h"
 
 class DataStoreHost {
 public:
@@ -45,6 +46,15 @@ public:
   // deleted slot is simply absent from the file, not written as empty).
   bool loadChannels(DataStoreHost* host);
   void saveChannels(DataStoreHost* host);
+  // /scopes1: the shared named-scope list (see ScopeList.h). `prefs` is only
+  // read, for a one-time migration of a pre-existing single
+  // default_scope_name/key into list entry 1 -- the file is authoritative
+  // once it exists. Returns true if the file existed or the migration ran
+  // (i.e. `list` reflects real prior configuration); false only means a
+  // genuinely fresh, unconfigured device (list left at its default: empty,
+  // default_idx 0 == "*").
+  bool loadScopeList(ScopeList& list, const NodePrefs& prefs);
+  void saveScopeList(const ScopeList& list);
   void migrateToSecondaryFS();
   uint8_t getBlobByKey(const uint8_t key[], int key_len, uint8_t dest_buf[]);
   bool putBlobByKey(const uint8_t key[], int key_len, const uint8_t src_buf[], uint8_t len);