Split ChatNostrCoordinator into owned components along domain boundaries

The 1,109-line coordinator becomes a 187-line facade wiring three
components, each with its own narrow context protocol:
GeohashSubscriptionManager (384 lines - subscription IDs + relay
lifecycle, the only NostrRelayManager toucher), NostrInboundPipeline
(490 lines - the hot event path, dedup-before-verify ordering preserved
verbatim), and GeoPresenceTracker (192 lines - teleport detection,
sampling LRU, notification cooldowns, now directly tested).

Perf baselines confirm the hot path is unchanged: fresh events
2,131 -> 2,138/sec, duplicates ~1.41M/sec.

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

bitchat/ViewModels/Extensions/ChatViewModel+Nostr.swift

@@ -12,86 +12,86 @@ extension ChatViewModel {
 
     @MainActor
     func resubscribeCurrentGeohash() {
-        nostrCoordinator.resubscribeCurrentGeohash()
+        nostrCoordinator.subscriptions.resubscribeCurrentGeohash()
     }
 
     @MainActor
     func subscribeNostrEvent(_ event: NostrEvent) {
-        nostrCoordinator.subscribeNostrEvent(event)
+        nostrCoordinator.inbound.subscribeNostrEvent(event)
     }
 
     @MainActor
     func subscribeGiftWrap(_ giftWrap: NostrEvent, id: NostrIdentity) {
-        nostrCoordinator.subscribeGiftWrap(giftWrap, id: id)
+        nostrCoordinator.inbound.subscribeGiftWrap(giftWrap, id: id)
     }
 
     @MainActor
     func switchLocationChannel(to channel: ChannelID) {
-        nostrCoordinator.switchLocationChannel(to: channel)
+        nostrCoordinator.subscriptions.switchLocationChannel(to: channel)
     }
 
     @MainActor
     func handleNostrEvent(_ event: NostrEvent) {
-        nostrCoordinator.handleNostrEvent(event)
+        nostrCoordinator.inbound.handleNostrEvent(event)
     }
 
     @MainActor
     func subscribeToGeoChat(_ ch: GeohashChannel) {
-        nostrCoordinator.subscribeToGeoChat(ch)
+        nostrCoordinator.subscriptions.subscribeToGeoChat(ch)
     }
 
     @MainActor
     func handleGiftWrap(_ giftWrap: NostrEvent, id: NostrIdentity) {
-        nostrCoordinator.handleGiftWrap(giftWrap, id: id)
+        nostrCoordinator.inbound.handleGiftWrap(giftWrap, id: id)
     }
 
     @MainActor
     func sendGeohash(context: GeoOutgoingContext) {
-        nostrCoordinator.sendGeohash(context: context)
+        nostrCoordinator.subscriptions.sendGeohash(context: context)
     }
 
     @MainActor
     func beginGeohashSampling(for geohashes: [String]) {
-        nostrCoordinator.beginGeohashSampling(for: geohashes)
+        nostrCoordinator.subscriptions.beginGeohashSampling(for: geohashes)
     }
 
     @MainActor
     func subscribe(_ gh: String) {
-        nostrCoordinator.subscribe(gh)
+        nostrCoordinator.subscriptions.subscribe(gh)
     }
 
     @MainActor
     func subscribeNostrEvent(_ event: NostrEvent, gh: String) {
-        nostrCoordinator.subscribeNostrEvent(event, gh: gh)
+        nostrCoordinator.presence.subscribeNostrEvent(event, gh: gh)
     }
 
     @MainActor
     func cooldownPerGeohash(_ gh: String, content: String, event: NostrEvent) {
-        nostrCoordinator.cooldownPerGeohash(gh, content: content, event: event)
+        nostrCoordinator.presence.cooldownPerGeohash(gh, content: content, event: event)
     }
 
     @MainActor
     func endGeohashSampling() {
-        nostrCoordinator.endGeohashSampling()
+        nostrCoordinator.subscriptions.endGeohashSampling()
     }
 
     @MainActor
     func setupNostrMessageHandling() {
-        nostrCoordinator.setupNostrMessageHandling()
+        nostrCoordinator.subscriptions.setupNostrMessageHandling()
     }
 
     @MainActor
     func handleNostrMessage(_ giftWrap: NostrEvent) {
-        nostrCoordinator.handleNostrMessage(giftWrap)
+        nostrCoordinator.inbound.handleNostrMessage(giftWrap)
     }
 
     func processNostrMessage(_ giftWrap: NostrEvent) async {
-        await nostrCoordinator.processNostrMessage(giftWrap)
+        await nostrCoordinator.inbound.processNostrMessage(giftWrap)
     }
 
     @MainActor
     func findNoiseKey(for nostrPubkey: String) -> Data? {
-        nostrCoordinator.findNoiseKey(for: nostrPubkey)
+        nostrCoordinator.inbound.findNoiseKey(for: nostrPubkey)
     }
 
     @MainActor