SecureBit.chat - P2P Encrypted Messenger Files

Fixes duplicated chat output and a layout overflow in the message list.

Fixed

• Received file announced once, not many times. The per-transfer lock used a single if check, so when 3+ chunk operations queued on the same file they ran concurrently and broke assembly atomicity. The lock now serializes correctly and file assembly is idempotent — File received shows exactly once per file.
• No more duplicated connection-setup system messages (e.g. "Both parties confirmed!" and "Secure connection successfully established"). handleVerificationBothConfirmed now bails out if both confirmations were already recorded, so the message and the verified transition fire only once.
• DTLS fingerprint wraps inside the chat bubble. The message text column is a flex child with default min-width:auto, so the long unbroken fingerprint overflowed; added min-w-0 so it wraps.
• Site header, init banner, and manifest now report the current version.

Live: https://securebit-chat.fly.dev/