fix: backport upstream electrum sync fix (PR #4341)

[ovitrif]

Summary

• Backport critical Electrum sync fix from upstream rust-lightning PR #4341
• Bump version to 0.7.0-rc.18

Bug Fix

The ElectrumSyncClient was incorrectly treating mempool entries (height=0 or -1) from blockchain.scripthash.get_history as confirmed transactions. This caused get_merkle to fail since it cannot prove block inclusion for unconfirmed transactions, breaking sync for 0-conf channel funding transactions.

Changes

• Added [patch.crates-io] section pointing to ovitrif/rust-lightning@0.2-electrum-fix
• Version bump: 0.7.0-rc.17 → 0.7.0-rc.18
• Regenerated bindings

References

• Upstream fix: ElectrumSyncClient: Skip unconfirmed get_history entries lightningdevkit/rust-lightning#4341
• Upstream 0.2.1 backport PR (pending): [0.2] Backports and cut 0.2.1 lightningdevkit/rust-lightning#4344
• Fork diff: ovitrif/rust-lightning@0.2-base...ovitrif:rust-lightning:0.2-electrum-fix

Test plan

• cargo build succeeds
• Bindings regenerated

Release

• v0.7.0-rc.18

🤖 Generated with Claude Code

[ovitrif]

Release

• Release v0.7.0-rc.18

[ovitrif]

Going to merge after I open the android PR to integrate this and validate it