feat: Transaction sequence runner with automatic sequence numbers

[ARAPHI20]

Overview

This PR adds a Transaction Sequence Runner to the Stellar composer that models multi-step flows, computes sequence numbers automatically so dependent operations run in order, submits steps sequentially with configurable stop/continue-on-failure, and persists per-step results — reducing manual sequence-number math and errors in complex multi-operation flows.

Related Issue

Changes

🧩 Transaction Sequence Runner

• [ADD] apps/api/src/modules/composer/dto/transaction-sequence.dto.ts

  • Defines sequence payloads: steps, operations, source account, dependency references, and stopOnFailure.
  • Validates dependency references (e.g., previous step's resulting account) before submission.

• [ADD] apps/api/src/modules/composer/entities/transaction-sequence-run.entity.ts

  • Persists each run with step index, transaction hash, status, and next sequence number.

• [ADD] apps/api/src/database/migrations/1786000000000-create-transaction-sequence.ts

  • Creates the transaction_sequence_run table for sequence-run history.

• [MODIFY] Sequence execution engine

  • apps/api/src/modules/composer/composer.service.ts — fetches current sequence and increments per step for automatic numbering; submits steps in order; honors stop/continue-on-failure; resolves dependencies to prior step outputs.
  • apps/api/src/modules/composer/composer.controller.ts — exposes create/run/history endpoints and per-step result retrieval.
  • apps/api/src/modules/composer/composer.module.ts — wires the new DTO, entity, and service.

• [MODIFY] Composer UI / client

  • apps/web/src/components/tools/composer/index.tsx — adds Transaction Sequence mode with multi-step editor, dependency picker, stop-on-failure toggle, and per-step result display.
  • apps/web/src/lib/composer-api.ts — adds createSequence, runSequence, and getSequenceHistory client methods.

• [ADD] apps/api/src/modules/composer/__tests__/transaction-sequence.service.test.ts

  • Coverage for correct sequence numbering, stop/continue on failure, dependency resolution, and history persistence.

Verification Results

npm test -- apps/api/src/modules/composer/__tests__/transaction-sequence.service.test.ts
✅ 16/16 passed

Live acceptance check:
✅ Sequence numbers computed automatically (current seq + 1 per step)
✅ Stop-on-failure halts at first failed step
✅ Continue-on-failure submits remaining steps and reports all statuses
✅ Dependency references resolved from prior step outputs
✅ Sequence runs persisted to history with per-step hash/status/next sequence

Acceptance Criteria	Status
Users can add multiple transactions to a sequence	✅ Multi-step editor with add/remove/reorder in composer
Sequence numbers are computed automatically so steps run in order	✅ Current seq fetched and incremented per step
User can choose stop-on-failure vs continue-on-failure	✅ Per-run toggle in API and UI
Each step's result (hash, status, next sequence) is reported	✅ Per-step result rows after submission
Dependent sources can reference the prior step's output	✅ Dependency picker resolves prior-step accounts
Sequence runs are persisted to history	✅ transaction_sequence_run table + history endpoint
Validation rejects invalid dependency references before running	✅ Pre-flight validation rejects missing/circular refs
Tests cover: correct sequence numbering, stop/continue on failure, dependency resolution, history persistence	✅ 16 tests passing

Closes #154

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