Geohash Bookmarks + Rising‑Edge Notifications + Friendly Names (#538)

* Add geohash bookmarks: persistence, sampling integration, and UI\n\n- Add GeohashBookmarksStore with UserDefaults persistence and toggle API\n- Sample union of regional + bookmarked geohashes for activity notifications\n- LocationChannelsSheet: bookmark icons on nearby rows and a Bookmarked section\n- Header toolbar: toggle bookmark for current geohash\n- Tests: GeohashBookmarksStoreTests for normalization and persistence\n\nRationale: Bookmarked geohashes are always sampled for new activity notifications and quickly selectable from the sheet.

* Notifications: remove background 'new chats!' nudge; geohash activity only on zero→alive; mesh 'nearby' only on zero→alive\n\n- Geohash sampling: notify only when previous participant count in last 5m was zero, with 30s freshness gate\n- Suppress old sampled events after (re)subscribe\n- Remove channel inactivity nudge\n- Mesh: reset rising-edge gate immediately when peer list goes empty (strict zero→alive)

* Geohash notifications: ensure triggering message appears\n\n- On zero→alive sampling, pre-populate geoTimelines[gh] with the triggering message\n- Dedup on per-geohash timeline and UI messages by message ID to avoid duplicates after subscribe\n- Keeps participant update, block/self checks, and cooldown intact

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Co-authored-by: jack <jackjackbits@users.noreply.github.com>

bitchat/Views/ContentView.swift

@@ -24,6 +24,7 @@ struct ContentView: View {
     
     @EnvironmentObject var viewModel: ChatViewModel
     @ObservedObject private var locationManager = LocationChannelManager.shared
+    @ObservedObject private var bookmarks = GeohashBookmarksStore.shared
     @State private var messageText = ""
     @State private var textFieldSelection: NSRange? = nil
     @FocusState private var isTextFieldFocused: Bool
@@ -1118,6 +1119,15 @@ struct ContentView: View {
                     .buttonStyle(.plain)
                     .accessibilityLabel("Open unread private chat")
                 }
+                // Bookmark toggle for current geohash (not shown for mesh)
+                if case .location(let ch) = locationManager.selectedChannel {
+                    Button(action: { GeohashBookmarksStore.shared.toggle(ch.geohash) }) {
+                        Image(systemName: GeohashBookmarksStore.shared.isBookmarked(ch.geohash) ? "bookmark.fill" : "bookmark")
+                            .font(.system(size: 12))
+                    }
+                    .buttonStyle(.plain)
+                    .accessibilityLabel("Toggle bookmark for #\(ch.geohash)")
+                }
                 // Location channels button '#'
                 Button(action: { showLocationChannelsSheet = true }) {
                     let badgeText: String = {