Encrypt private media before BLE fragmentation (#1434)

Closes the last cleartext private-content path over BLE: private DM images/voice were sent as plaintext signed fileTransfer packets, TTL-relayed across the mesh, so every relay saw the full bytes. Now the complete BitchatFilePacket is encrypted as a single Noise AEAD message (inner type 0x20, matching Android) and the opaque ciphertext is fragmented. Adds an authenticated in-session capability proof (0x21 TLV: capabilities + Ed25519 key), TOFU-style downgrade pinning, a per-send consent dialog for the signed-cleartext fallback to legacy peers, and a cancellation/admission registry so cancel/delete cannot race a deferred cleartext send.

Android wire constants (0x20 / 0x21 / capability bit 8) confirmed shipping. The 256-fragment preflight cap applies only to the directed fileTransfer migration fallback; encrypted media to capable peers uses the full receiver ceiling.

Rebased over #1428/#1349: identity reads go through BLELocalIdentityStateStore; the session-bound authenticated signing-key check and the announce-path TOFU pin are kept as complementary checks. Full local suite green (1744+197 tests).

bitchatTests/Services/BLENoiseSessionQueuesTests.swift

@@ -48,7 +48,10 @@ struct BLENoiseSessionQueuesTests {
         queues.appendTypedPayload(Data([0x01]), for: peerID)
         queues.appendTypedPayload(Data([0x02]), for: peerID)
 
-        #expect(queues.takeTypedPayloads(for: peerID) == [Data([0x01]), Data([0x02])])
+        #expect(queues.takeTypedPayloads(for: peerID) == [
+            BLEPendingTypedPayload(payload: Data([0x01]), transferId: nil),
+            BLEPendingTypedPayload(payload: Data([0x02]), transferId: nil)
+        ])
         #expect(queues.takeTypedPayloads(for: peerID).isEmpty)
         #expect(queues.takePrivateMessages(for: peerID).map(\.messageID) == ["m1"])
     }
@@ -64,4 +67,21 @@ struct BLENoiseSessionQueuesTests {
 
         #expect(queues.isEmpty)
     }
+
+    @Test
+    func transferIDSurvivesHandshakeQueueAndCanBeCancelledBeforeDrain() {
+        let peerID = PeerID(str: "aaaaaaaaaaaaaaaa")
+        var queues = BLENoiseSessionQueues()
+
+        queues.appendTypedPayload(Data([0x20, 0xAA]), transferId: "media-1", for: peerID)
+        queues.appendTypedPayload(Data([0x01, 0xBB]), for: peerID)
+
+        let removed = queues.removeTypedPayload(transferId: "media-1")
+        let removedAgain = queues.removeTypedPayload(transferId: "media-1")
+        #expect(removed)
+        #expect(!removedAgain)
+        #expect(queues.takeTypedPayloads(for: peerID) == [
+            BLEPendingTypedPayload(payload: Data([0x01, 0xBB]), transferId: nil)
+        ])
+    }
 }