fix/unified payment bolt12 duplicate fallback

[Bartok9]

• fix(close_channel): error when no matching channel found
  Closes close_channel returns Ok when no channel matches the user_channel_id #1084

  Previously close_channel and force_close_channel returned Ok(()) when
  no matching UserChannelId was found for the counterparty, silently
  succeeding without initiating a close. Now returns Err(ChannelClosingFailed),
  matching update_channel_config.

  AI-assisted: generated by Sera (Hermes Agent), verified manually.
  Tests compile; integration test requires bitcoind/electrs binaries
  (architecturally incompatible electrs binary in this cron environment,
  same failure affects all integration tests)

  Signed-off-by: Bartok9 259807879+Bartok9@users.noreply.github.com

• fix: BOLT12 arm of UnifiedPayment::send returns DuplicatePayment/PersistenceFailed errors
  The BOLT12 arm of UnifiedPayment::send was using a .map_err() + if let Ok pattern
  that caused Critical errors (DuplicatePayment, PersistenceFailed) to fall through to the
  BOLT11/onchain payment methods. This could result in double-payment if:

  1. A BOLT12 payment fails with PersistenceFailed (e.g., payment store insert fails after
     ChannelManager accepted the payment)
  2. The code falls through to BOLT11 attempt
  3. BOLT11 also fails with PersistenceFailed
  4. The code falls through to on-chain broadcast
  5. User is charged twice (once via Lightning, once via on-chain)

  This fix mirrors the BOLT11 arm fix in PR Fix BOLT11 DuplicatePayment triggering on-chain fallback in unified payment #1038. Both DuplicatePayment and
  PersistenceFailed are now terminal errors that abort the unified payment entirely.

  Fixes: BOLT12 leg falls through to BOLT11/on-chain on already-initiated errors #1060

[ldk-reviews-bot]

I've assigned @tnull as a reviewer!
I'll wait for their review and will help manage the review process.
Once they submit their review, I'll check if a second reviewer would be helpful.

[tnull]

The two issues addressed are not even related. Please don't just mix arbitrary issues in one PR.