Persist authenticated private-media delivery receipts (#1466)

Adds a durable receiver-side ledger (BLEPrivateMediaReceiptStore) mapping a deterministic private-media message ID — hash-bound to sender, recipient, and entropy-bearing filename — to the stored file before UI delivery and before the Noise-encrypted delivery ACK, so sender retries and relaunches cannot create duplicate bubbles or files. Receipts are unforgeable without the Noise session; capability bit 9 rides the existing announce bitfield (no wire-format change; rolling upgrade safe both directions).

Includes review fixes: corrupt receipt records are quarantined per-record (bytes preserved at <id>.json.corrupt, only that ID fail-closed — previously one bad record silently disabled ALL inbound private media forever); the panic reset now reaches BLEService's own store instance via completePanicReset with a production-wiring test; and both content.delivery.reason.* strings ship with full 30-locale coverage.

bitchatTests/Services/BLENoiseReconnectPolicyTests.swift

@@ -111,5 +111,8 @@ struct BLENoiseReconnectPolicyTests {
             )
         )
         #expect(PeerCapabilities.localSupported.contains(.privateMedia))
+        #expect(
+            PeerCapabilities.localSupported.contains(.privateMediaReceipts)
+        )
     }
 }