add debug and trace logs across funding flow

[doitian]

Summary

Adds structured debug and trace level logs throughout the funding flow so
that channel-open failures can be diagnosed without reproducing under a
debugger. Previously, failures only surfaced at the retry scheduler with
the bare FundingError, leaving operators to guess which stage went
wrong (cell collection, balancing, signing, peer verification, broadcast,
or tracing).

Changes

• ckb/funding/funding_tx.rs
  • Log entry context for FundingTxBuilder::build, build_funding_cell,
    build_udt_inputs_outputs, build_base_from_funding_cell, and
    build_and_balance_tx (amounts, reserves, fee rate, source lock hash,
    tip block, exclusion-map size).
  • Identify which checked_add overflowed in build_funding_cell.
  • Trace per-batch UDT cell collection and emit a debug log on the
    "insufficient UDT cells" path showing exact found vs needed.
  • Log balanced tx hash + input/output/cell-dep counts.
  • Log signing entry/exit and peer tx verification context with both
    local and remote tx hashes and counts.
• ckb/actor.rs — Fund, BuildUnsignedFundingTx, VerifyFundingTx,
  Sign, and SendTx handlers now log requests and outcomes.
• fiber/in_flight_ckb_tx_actor.rs — derive Debug for
  InFlightCkbTxKind and include tx_hash + tx_kind in start,
  send_tx_interval, send_tx, and report_tracing_result logs.
• fiber/network.rs — add entry context (channel_id, attempt,
  amounts, target peer, tx_hash) for do_update_channel_funding,
  do_sign_funding_tx, fund, send_tx, and abort_funding.

Verification

• cargo check -p fnn -p fiber-bin
• cargo clippy --all-targets --all-features -p fnn -p fiber-bin -- -D warnings
• cargo fmt --all

No behavioral changes; only logging additions and a single derived
Debug impl.

---

This PR description was generated with AI assistance.

[chenyukang]

Reviewed the changes and found no blocking issues.