core: send badge ZK-proofs to XFTP servers, add file expiry time - #7430

Two orthogonal changes: (1) send badge/entitlement ZK-proofs to XFTP servers via the updated xftpSendFile credential argument, and (2) surface the server-granted file storage expiry to sender and recipients.

I traced the file-expiry change end to end and it is consistent:

• XMsgFileDescr gains an optional fileExpires; encode uses .=?, decode uses opt, no version bump — older peers omit/skip it. All 8 constructor/pattern sites are updated.
• CIFile gains fileExpires :: Maybe UTCTime; the files.file_expires_at column is added with matching SQLite/Postgres migrations and schema snapshots, and read back in exactly the three CIFile-bearing queries (getDirectChatItem, getGroupChatItem, getLocalChatItem) — MaybeCIFIleRow and all three to*ChatItem parsers stay in sync, and those parsers have no other callers, so no query is left selecting the wrong column count.
• Sender path stores the granted expiry from SFDONE (GSTExpires epochSeconds → UTCTime) via setSndFTPrivateSndDescr and threads it into every XMsgFileDescr; recipient path stores the received expiry via setFileExpiration inside the same transaction as appendRcvFD. All the transient CIFile { fileExpires = Nothing } constructions are pre-descriptor states that are re-read from the DB when displayed — correct.
• Client side (iOS/Kotlin) derives expired from fileExpires < now, gates the rcvInvitation icon and showFileErrorAlert on it, and both FileError types are Equatable/sealed as needed. SDK type files (TS/Python/TYPES.md) are updated. Strings added.

Two behavioral notes, not blocking:

• The recipient's expiry is stored on XMsgFileDescr receipt but no chat-item update event is emitted at that point, so the expiry icon/info only appears after the item is next loaded. Matches the plan; acceptable.
• Kotlin's val expired is computed eagerly at construction against Clock.System.now(), so it is a snapshot per load (iOS recomputes per access). A file that expires while the view is open won't flip until reload. Minor.

The badge/entitlement change swaps the hardcoded badgePublicKeys map and bbsBadgeHeader for entitlementIssuerKeys / entitlementBBSHeader from the bumped simplexmq, and adds badgeServerCredential. Correctness of the header constant and key set depends on the paired simplexmq tag (6541745f…), which I could not inspect from this repo — assuming that side matches, the wiring here is straightforward.

One trivial nit inline (import ordering). Otherwise this is a clean, minimal, well-scoped change.