feat: initialize project backend structure and document system specifications across all modules

docs/specs/reward_campaign/ols_transaction_code.md

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+---
+title: "OLS Transaction Code"
+type: OpenSpec
+status: Draft
+domain: Reward Campaign Management
+---
+
+# OLS Transaction Code
+
+## Requirement Definition
+Every transaction processed against Campaign Rules must have an OLS Transaction Code (TC). It acts as the primary key to locate relevant Campaign Rules.
+
+## Process Flow
+
+### Pre-Conditions
+- Users must have access rights in the module.
+
+## Business Rules
+
+### Data Schema
+
+| Field Name | Description | Logic Type | Constraints / Rules |
+|---|---|---|---|
+| OLS Transaction Code | The internal transaction code. | String (10) | Required. |
+| Description | Description of the code. | String (30) | Required. |
+| External Transaction Code | The mapped external TCs. | List of Strings | Optional. Many External TCs can map to one OLS TC. |
+| Reversal Indicator | Indicates if this is a reversal. | Boolean | Default False. |
+
+### Execution
+- Supports internal transactions (e.g., CEP Batch generated) that do not have an External TC.
+- Supports Maker-Checker approval workflow (Pending -> Active).
+
+## Exception Flow
+- N/A