Inject notification/favorites singletons through coordinator contexts

NotificationService.shared and FavoritesPersistenceService.shared
accesses across nine coordinators/components consolidate into
ChatViewModel witnesses behind intent-named context members
(notifyPrivateMessage, notifyMention, favoriteRelationship(forNoiseKey:),
allFavoriteRelationships, postLocalNotification, ...). Singleton reach
from coordinators is now zero; nine new tests cover previously
untestable notification/favorites flows.

Also root-causes the long-flaky gift-wrap dedup test: parallel tests
share LocationChannelManager.shared, so channel-switch tests trigger
clearProcessedNostrEvents() on every live ChatViewModel, wiping the
dedup record mid-test. The invariant (forged-signature copies never
poison dedup) now lives as a deterministic NostrInboundPipeline
mock-context test; two Schnorr concurrency probes added along the way
stay as regression guards for the P256K shared-context assumptions.

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

bitchatTests/ChatVerificationCoordinatorContextTests.swift

@@ -7,11 +7,12 @@
 // `ChatViewModel`, following the `ChatDeliveryCoordinatorContextTests` /
 // `ChatPrivateConversationCoordinatorContextTests` exemplars.
 //
-// Scope note: `handleVerifyResponsePayload` requires a real Ed25519 signature
-// and posts via `NotificationService.shared`; it remains covered by the full
-// view-model/integration tests. Challenge handling, QR kickoff, fingerprint
-// verification, and verified-set loading are covered here
-// (`VerificationService.shared` is only used for pure payload build/parse).
+// Scope note: `handleVerifyResponsePayload` requires a real Ed25519
+// signature; it remains covered by the full view-model/integration tests.
+// Challenge handling, QR kickoff, fingerprint verification, verified-set
+// loading, and the mutual-verification notification (posted through the
+// injected context) are covered here (`VerificationService.shared` is only
+// used for pure payload build/parse).
 //
 
 import Testing
@@ -117,6 +118,13 @@ private final class MockChatVerificationContext: ChatVerificationContext {
     func sendVerifyResponse(to peerID: PeerID, noiseKeyHex: String, nonceA: Data) {
         sentResponses.append((peerID, noiseKeyHex, nonceA))
     }
+
+    // Notifications
+    private(set) var postedLocalNotifications: [(title: String, body: String, identifier: String)] = []
+
+    func postLocalNotification(title: String, body: String, identifier: String) {
+        postedLocalNotifications.append((title, body, identifier))
+    }
 }
 
 // MARK: - Helpers
@@ -272,6 +280,35 @@ struct ChatVerificationCoordinatorContextTests {
         await waitForMainQueue()
         #expect(context.encryptionStatuses[peerID] == .noiseHandshaking)
     }
+
+    @Test @MainActor
+    func handleVerifyChallengePayload_postsMutualVerificationToastOncePerMinute() async {
+        let context = MockChatVerificationContext()
+        let coordinator = ChatVerificationCoordinator(context: context)
+        let peerID = PeerID(str: "1122334455667788")
+        let myHex = context.myNoiseStaticKey.hexEncodedString()
+        context.fingerprintsByPeerID[peerID] = "fp-mutual"
+        context.verifiedFingerprints = ["fp-mutual"]
+
+        coordinator.handleVerifyChallengePayload(
+            from: peerID,
+            payload: makeVerifyChallengeTLV(noiseKeyHex: myHex, nonceA: Data(repeating: 0x07, count: 16))
+        )
+
+        // Already-verified peer challenging us: mutual-verification toast.
+        #expect(context.postedLocalNotifications.count == 1)
+        #expect(context.postedLocalNotifications.first?.title == "Mutual verification")
+        #expect(context.postedLocalNotifications.first?.body.hasSuffix("verified each other") == true)
+        #expect(context.postedLocalNotifications.first?.identifier.hasPrefix("verify-mutual-") == true)
+
+        // A fresh nonce inside the per-fingerprint toast cooldown stays silent.
+        coordinator.handleVerifyChallengePayload(
+            from: peerID,
+            payload: makeVerifyChallengeTLV(noiseKeyHex: myHex, nonceA: Data(repeating: 0x08, count: 16))
+        )
+        #expect(context.postedLocalNotifications.count == 1)
+        #expect(context.sentResponses.count == 2)
+    }
 }
 
 /// The installed callbacks hop through `DispatchQueue.main.async`; tests must