feat: multi-hop fiber payments for cch

[doitian]

Important

Stack PR based on #945

CCH is added before multi-hop payments so it manipulates TLC directly
for fiber payments.

This PR adds multi-hop payments support to CCH.

Differences with #615 :

• This PR does not use store change event to monitor fiber payments and invoices. Such change will be included in a new PR.
• This PR uses HoldTlc instead of a new database type InvoiceChannelInfo to store incoming payments to hold invoices.
• This PR includes the refactoring in feat: cch persistence #898 to uniform SendBTCOrder and ReceiveBTCOrder into CchOrder.

[Copilot]

Pull Request Overview

This PR refactors the cross-chain hub (CCH) implementation to support bidirectional BTC-CKB swaps using a unified order structure. The changes consolidate the separate SendBTC and ReceiveBTC order types into a single CchOrder type, introduce hold invoice support, and improve the payment flow.

Key Changes

• Unified order management: Merged SendBTCOrder and ReceiveBTCOrder into a single CchOrder struct with a CchInvoice enum to handle both Lightning and Fiber invoices
• Added hold invoice support: Introduced settle_invoice RPC method and related error handling to manually settle hold invoices
• Simplified payment flow: Refactored RPC methods (renamed get_receive_btc_order to get_cch_order) and updated test files to reflect new API

Reviewed Changes

Copilot reviewed 27 out of 27 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
crates/fiber-lib/src/cch/order.rs	Unified order types into CchOrder and added CchInvoice enum for handling both network types
crates/fiber-lib/src/cch/actor.rs	Major refactor of CCH actor implementation with unified order processing and network actor integration
crates/fiber-lib/src/cch/orders_db.rs	Simplified database methods to work with unified CchOrder type
crates/fiber-lib/src/rpc/invoice.rs	Added settle_invoice RPC method and modified new_invoice to support optional preimage/hash parameters
crates/fiber-lib/src/rpc/cch.rs	Updated RPC interfaces to use CchOrderResponse and simplified parameter structures
crates/fiber-lib/src/fiber/network.rs	Added AddInvoice and SettleInvoice commands to network actor
crates/fiber-lib/src/fiber/channel.rs	Added hold TLC support for invoices without preimages
tests/bruno/e2e/cross-chain-hub/*.bru	Updated e2e test suite to reflect new API and workflow
docs/biscuit-auth.md	Updated authorization rules for renamed RPC methods

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