feat(indexer): outgoing channel primitives

[m-kus]

TL;DR

Added support for outgoing channels in the privacy pool implementation, enabling recipient address encryption and decryption.

What changed?

• Added new types and functions to support outgoing channels:

  • Created EncOutgoingChannelInfo struct to store encrypted recipient information
  • Implemented decrypt_outgoing_recipient_addr function to decrypt recipient addresses
  • Added hash functions for channel key derivation, outgoing channel ID computation, and recipient address encryption
  • Added storage slots for encrypted outgoing channel information
  • Extended the IViews trait with a get_outgoing_channel_info method

• Added new domain separation tags:

  • CHANNEL_KEY_TAG
  • OUTGOING_CHANNEL_ID_TAG
  • ENC_RECIPIENT_ADDR_TAG

• Added comprehensive test coverage for all new functionality

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This change is 

[m-kus]

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Learn more

• feat(indexer): e2e discovery flow #440
• feat(indexer): preflight endpoint, sync with abstract discovery provider interface #439
• feat(indexer): outgoing state sync endpoint #438
• feat(indexer): batch state sync #435
• feat(indexer): sync outgoing state #433
• feat(indexer): discover outgoing channels #430
• feat(indexer): find last used note index #429
• feat(indexer): outgoing channel primitives #424 👈 (View in Graphite)
• feat(indexer): filter out spent notes, use secret felt #422
• feat: scaffold e2e testing harness, move devnet dump generation to a separate script #421
• feat(indexer): sync code and spec, update guidelines and todos #414
• feat(indexer): add incoming state sync endpoint #413
• feat(indexer): api error types #412
• refactor(indexer): common helpers for spawning devnet/indexer #411
• feat(indexer): incoming state sync orchestration #410
• feat(indexer): cursor pagination for discovery #408
• refactor(indexer): reorganize discovery-core, prepare for state sync #407 : 1 other dependent PR (#453 )
• feat(ci): speed up rust workflow #415
• main

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