Fixed issue bug] handle re orgs for event indexing

backend/docs/specs/stellar_ingestion/checklist.md

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+# Checklist
+
+- [x] `indexer_state` table created via migration (Sequelize Model defined).
+- [x] `IndexerState` model implemented.
+- [x] `SubSchedule` model updated with `block_number`.
+- [x] `StellarIngestionService` implemented.
+- [x] `rollbackToLedger` successfully deletes "future" records.
+- [x] `indexer_state` updates correctly after ingestion/rollback.
+- [x] Unit tests passing for rollback scenarios.

backend/docs/specs/stellar_ingestion/spec.md

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+# Stellar Ingestion & Re-org Handling Specification
+
+## Overview
+This feature implements robust Stellar ledger ingestion with protection against network re-orgs (forks). It ensures that deposits (vault top-ups) and claims are not double-counted if the network reorganizes.
+
+## Requirements
+1.  **State Tracking**: Store the `last_ingested_ledger` sequence number in the database.
+2.  **Re-org Detection**: Detect when the local chain tip diverges from the network (not applicable for simple forward-sync, but necessary for robustness).
+3.  **Rollback Logic**: Ability to revert database changes (claims, deposits) that occurred after a specific ledger sequence.
+4.  **Idempotency**: Ensure processing the same ledger twice does not result in duplicate data.
+
+## Architecture
+
+### Database Schema
+New table `indexer_state` to track ingestion progress:
+```sql
+CREATE TABLE indexer_state (
+  service_name VARCHAR(50) PRIMARY KEY,
+  last_ingested_ledger BIGINT NOT NULL,
+  updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+);
+```
+
+### Components
+1.  **`src/services/stellarIngestionService.js`**:
+    -   Manages the ingestion loop (polling or streaming).
+    -   Checks for re-orgs (simulated or actual if using a horizon instance).
+    -   Orchestrates the rollback process.
+2.  **`src/models/indexerState.js`**: Sequelize model for `indexer_state`.
+3.  **Rollback Methods**:
+    -   `ClaimsHistory.destroy({ where: { block_number: { [Op.gt]: targetLedger } } })`
+    -   `SubSchedule.destroy({ where: { block_number: { [Op.gt]: targetLedger } } })` (Note: `block_number` needs to be added to `SubSchedule` if missing).
+
+## Data Flow
+1.  **Ingestion**:
+    -   Fetch next ledger from Stellar Horizon/RPC.
+    -   Process transactions (deposits/claims).
+    -   Update `indexer_state` with `last_ingested_ledger`.
+    -   Commit transaction.
+
+2.  **Re-org Handling (Rollback)**:
+    -   If a re-org is detected (e.g., current ledger parent hash != stored last ledger hash - *advanced, for now we will implement the rollback mechanism triggered manually or by specific error*), or if we need to re-process:
+    -   Call `rollbackToLedger(targetSequence)`.
+    -   Delete all `ClaimsHistory` and `SubSchedule` records with `block_number > targetSequence`.
+    -   Update `indexer_state` to `targetSequence`.
+
+## Configuration
+-   `STELLAR_HORIZON_URL`: URL of the Stellar Horizon instance.
+-   `STARTING_LEDGER`: Ledger sequence to start ingestion from (if state is empty).

backend/docs/specs/stellar_ingestion/tasks.md

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+# Tasks
+
+1.  [x] Create migration for `indexer_state` table. (Handled via Sequelize sync in `models/index.js` but model definition created)
+2.  [x] Create `src/models/indexerState.js` model.
+3.  [x] Add `block_number` (ledger sequence) column to `SubSchedule` model/table if it doesn't exist (it exists in `ClaimsHistory`).
+4.  [x] Create `src/services/stellarIngestionService.js` with:
+    -   `getLastIngestedLedger()`
+    -   `updateLastIngestedLedger(sequence)`
+    -   `rollbackToLedger(sequence)`
+5.  [x] Implement `rollbackToLedger` logic to delete records from `ClaimsHistory` and `SubSchedule` greater than the target ledger.
+6.  [x] Add unit tests for `stellarIngestionService` specifically testing the rollback logic.