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/Services/TransportConfig.swift

@@ -100,8 +100,14 @@ enum TransportConfig {
 
     // Location
     static let locationDistanceFilterMeters: Double = 1000
+    // Live (channel sheet open) distance threshold for meaningful updates
+    static let locationDistanceFilterLiveMeters: Double = 21.0
     static let locationLiveRefreshInterval: TimeInterval = 5.0
 
+    // Notifications (geohash)
+    static let uiGeoNotifyCooldownSeconds: TimeInterval = 60.0
+    static let uiGeoNotifySnippetMaxLen: Int = 80
+
     // Nostr geohash
     static let nostrGeohashInitialLookbackSeconds: TimeInterval = 3600
     static let nostrGeohashInitialLimit: Int = 200
@@ -169,6 +175,10 @@ enum TransportConfig {
     // UI color tuning
     static let uiColorHueAvoidanceDelta: Double = 0.05
     static let uiColorHueOffset: Double = 0.12
+    // Peer list palette
+    static let uiPeerPaletteSlots: Int = 36
+    static let uiPeerPaletteRingBrightnessDeltaLight: Double = 0.07
+    static let uiPeerPaletteRingBrightnessDeltaDark: Double = -0.07
 
     // UI windowing (infinite scroll)
     static let uiWindowInitialCountPublic: Int = 300