fix: NEP-245 multi-token support using token registry instead of RPC

[Copilot]

Summary

Fixes #25

NEP-245 multi-token IDs like intents.near:nep245:v2_1.omni.hot.tg:43114_111... contain multiple colons, causing AccountId parsing to fail when attempting RPC calls. The old code would strip the prefix and try to parse v2_1.omni.hot.tg:43114_... as an account ID.

Changes

• Token registry lookup (intents_tokens.rs): Added DEFUSE_TOKENS_MAP_CELL HashMap and find_token_by_defuse_asset_id() for O(1) lookups by defuseAssetId
• Metadata fetching (counterparty.rs): Modified ensure_ft_metadata() to detect all intents.near:* tokens and use registry instead of RPC calls
• Tests: Added unit tests for NEP-245/NEP-141 token lookups

Test Plan

cargo test --test nep245_token_registry_test

Example

// Before: AccountId parsing error
ensure_ft_metadata("intents.near:nep245:v2_1.omni.hot.tg:137_...")
  → extract_ft_contract() → "v2_1.omni.hot.tg:137_..." (still has colon!)
  → AccountId::from_str() → ERROR

// After: Registry lookup
ensure_ft_metadata("intents.near:nep245:v2_1.omni.hot.tg:137_...")
  → starts_with("intents.near:") → true
  → find_token_by_defuse_asset_id("nep245:v2_1.omni.hot.tg:137_...")
  → {symbol: "USDC", decimals: 6, ...}

All intents tokens (NEP-141 and NEP-245) now use the token registry from data/tokens.json. Regular FT tokens continue using RPC queries unchanged.

[petersalomonsen]

@race-of-sloths score 3

[petersalomonsen]

@akorchyn I have tested these changes manually, and it seems to work as intended

[race-of-sloths]

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Current status: executed

Reviewer	Score
@petersalomonsen	3

Your contribution is much appreciated with a final score of 3!
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@petersalomonsen received 25 Sloth Points for reviewing and scoring this pull request.

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