UI: diversify peer colors; smarter geo notifications; 21m live location (#531)

- Use minimal-distance hue palette for mesh and geohash lists; align chat sender colors with list palette.
- Add foreground geo notifications for different channels; deep-link to bitchat://geohash/<gh>; per-geohash 60s cooldown; respect self/blocks.
- Global geohash sampling runs outside the sheet; delegate handles deeplinks and suppresses when already in-channel.
- Switch location channel sheet to continuous CoreLocation with 21m distance filter; add config knob.
- Only link geohash hashtags when standalone (no @name#abcd or word#abcd).
- Include mesh-reachable peers in mesh counts and in "bitchatters nearby" notification.
- Add TransportConfig knobs for palette and geo notifications.

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

bitchat/BitchatApp.swift

@@ -173,6 +173,14 @@ class NotificationDelegate: NSObject, UNUserNotificationCenterDelegate {
                 }
             }
         }
+        // Handle deeplink (e.g., geohash activity)
+        if let deep = userInfo["deeplink"] as? String, let url = URL(string: deep) {
+            #if os(iOS)
+            DispatchQueue.main.async { UIApplication.shared.open(url) }
+            #else
+            DispatchQueue.main.async { NSWorkspace.shared.open(url) }
+            #endif
+        }
         
         completionHandler()
     }
@@ -192,6 +200,15 @@ class NotificationDelegate: NSObject, UNUserNotificationCenterDelegate {
                 }
             }
         }
+        // Suppress geohash activity notification if we're already in that geohash channel
+        if identifier.hasPrefix("geo-activity-"),
+           let deep = userInfo["deeplink"] as? String,
+           let gh = deep.components(separatedBy: "/").last {
+            if case .location(let ch) = LocationChannelManager.shared.selectedChannel, ch.geohash == gh {
+                completionHandler([])
+                return
+            }
+        }
         
         // Show notification in all other cases
         completionHandler([.banner, .sound])