feat: tracking headers

[klejeune]

---

Note

Add optional tracking headers to submitSignedTransactions to send X-Transaction-Feature and X-Transaction-Kind, with new enums/types and tests.

• SmartTransactionsController:
  • Extend private #fetch to accept trackingHeaders and include X-Transaction-Feature/X-Transaction-Kind when provided.
  • Update submitSignedTransactions signature to accept optional trackingHeaders and forward them to API calls.
• Types/Exports:
  • Add TransactionFeature, TransactionKind, and TransactionTrackingHeaders in types and export from index.
• Tests:
  • Add coverage ensuring headers are set correctly for feature/kind combinations, omitted when absent, and support all enum values.

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