Fix restore-path main↔bleQueue deadlock and courier drop amplification

A device froze permanently in a two-phone test. Debugger stacks showed an
ABBA deadlock: the main actor was in bleQueue.sync (delivery-ack send →
broadcastPacket → readLinkState) while bleQueue was in main.sync
(captureBluetoothStatus reading backgroundTimeRemaining). The load that
lined the two edges up came from a courier-drop amplification storm:
drop dedup was in-memory only while the outbox driving 120s re-deposits
is persisted, so every relaunch republished the same undelivered DM as a
fresh 24h relay drop and every gateway relaunch re-fetched the whole
backlog — ~20 copies of one DM delivered in 40ms, each triggering
decrypt + delivery + ack + handshake work.

Fixes, in rank order:
- Edge B (P0): captureBluetoothStatus no longer main.syncs from bleQueue;
  backgroundTimeRemaining is sampled on main and cached behind a lock.
  Invariant documented: bleQueue must NEVER sync-dispatch to main.
- Edge A (P0, defense in depth): sendDeliveryAck / sendReadReceipt /
  sendPrivateMessage / sendNoisePayload / triggerHandshake hop to
  messageQueue like sendMessage, so no main-actor call path reaches
  readLinkState's bleQueue.sync.
- Drop dedup (P1): publishedDropKeys and seenDropEventIDs persist across
  relaunches (new BridgeDropDedupStore, entries expire with the 24h
  NIP-40 drop window; wiped on panic) — one drop per message ID per 24h
  regardless of relaunch count.
- Receiver dedup (P1): openCourierEnvelope dedups on the inner private
  message ID before delivery, so a duplicate copy costs one decrypt and
  never re-delivers, re-acks, or re-triggers a handshake.
- Handshake gating (P2): queued acks initiate a Noise handshake only for
  reachable peers; mail from absent/rotated identities no longer turns
  each copy into a mesh-wide handshake flood (the ack stays queued and
  flushes when a session eventually establishes).
- Outbox (P3): re-enqueueing a queued message ID carries over its
  depositedCourierKeys so resends stop re-burning the same courier slots.

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

bitchatTests/EndToEnd/PrekeyEndToEndTests.swift

@@ -190,7 +190,11 @@ struct PrekeyEndToEndTests {
         #expect(message.content == "burn after reading")
 
         // 6. Redelivery tolerance: the same envelope arriving via another
-        //    packet (spray-and-wait) still opens inside the grace window.
+        //    packet (spray-and-wait) still decrypts inside the prekey grace
+        //    window (asserted at the crypto layer in NoisePrekeyTests), but
+        //    the duplicate is absorbed before delivery — the receiver dedups
+        //    on the inner message ID, so redundant courier copies never
+        //    re-deliver (or re-ack) the same message.
         let redelivery = BitchatPacket(
             type: MessageType.courierEnvelope.rawValue,
             senderID: Data(hexString: carol.myPeerID.id) ?? Data(),
@@ -203,9 +207,10 @@ struct PrekeyEndToEndTests {
         bob._test_handlePacket(redelivery, fromPeerID: carol.myPeerID)
         let redelivered = await TestHelpers.waitUntil(
             { bobDelegate.snapshot().count == 2 },
-            timeout: TestConstants.defaultTimeout
+            timeout: TestConstants.shortTimeout
         )
-        #expect(redelivered)
+        #expect(!redelivered)
+        #expect(bobDelegate.snapshot().count == 1)
     }
 
     @Test func withoutBundleSealingFallsBackToStatic() async throws {