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/ChatViewModelExtensionsTests.swift

@@ -398,40 +398,6 @@ struct ChatViewModelNostrExtensionTests {
         #expect(viewModel.privateChats.isEmpty)
     }
 
-    @Test @MainActor
-    func handleNostrMessage_invalidSignatureDoesNotPoisonDedup() async throws {
-        let (viewModel, _) = makeTestableViewModel()
-        let sender = try NostrIdentity.generate()
-        let recipient = try #require(try viewModel.idBridge.getCurrentNostrIdentity())
-        let giftWrap = try NostrProtocol.createPrivateMessage(
-            content: "verify:noop",
-            recipientPubkey: recipient.publicKeyHex,
-            senderIdentity: sender
-        )
-        var invalidGiftWrap = giftWrap
-        invalidGiftWrap.sig = String(repeating: "0", count: 128)
-
-        // Verification and recording now happen on a detached task; give the
-        // invalid copy time to be verified-and-rejected, then assert it never
-        // entered the dedup set.
-        viewModel.handleNostrMessage(invalidGiftWrap)
-        try await Task.sleep(nanoseconds: 150_000_000)
-        #expect(!viewModel.deduplicationService.hasProcessedNostrEvent(giftWrap.id))
-
-        // Generous deadline: the detached verification task can be starved
-        // under parallel test load.
-        viewModel.handleNostrMessage(giftWrap)
-        var recorded = false
-        for _ in 0..<600 {
-            if viewModel.deduplicationService.hasProcessedNostrEvent(giftWrap.id) {
-                recorded = true
-                break
-            }
-            try await Task.sleep(nanoseconds: 10_000_000)
-        }
-        #expect(recorded)
-    }
-
     @Test @MainActor
     func switchLocationChannel_clearsNostrDedupCache() async {
         let (viewModel, _) = makeTestableViewModel()