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

docs/specs/reward_campaign/reward_campaign_rule.md

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+---
+title: "Reward Campaign Rule"
+type: OpenSpec
+status: Draft
+domain: Reward Campaign Management
+---
+
+# Reward Campaign Rule
+
+## Requirement Definition
+Campaign Rules define the business rules for giving a reward, defining conditions for redemption, or triggering batch updates (CEP/REP). This spec covers standard Award, Redeem, and Adjust rules.
+
+## Process Flow
+
+### Pre-Conditions
+- Users must have access rights.
+
+## Business Rules
+
+### Data Schema
+
+#### General Information
+| Field Name | Description | Logic Type | Constraints / Rules |
+|---|---|---|---|
+| Campaign ID | Parent campaign. | Enum (Lookup) | Required. |
+| Campaign Rule ID | System-generated identifier. | String (10) | Required. |
+| Campaign Rule Name | Name of the rule. | String (50) | Required. |
+| Rule Type | Award, Redeem, Adjust. | Enum (Lookup) | Required. |
+| Effective Date From | Start of effective period. | Date | Required. |
+| Effective Date To | End of effective period. | Date | Required. |
+
+#### Rule Setting
+| Field Name | Description | Logic Type | Constraints / Rules |
+|---|---|---|---|
+| Effective Period is Based On| Transaction Date vs Post Date. | Enum | Required. |
+| Pool | Reward pool applied to this rule. | Enum (Lookup) | Required. |
+| Item Code | eVoucher item if Pool Type is eVoucher. | Enum (Lookup) | Conditional. |
+| Message Template ID | SMS/Email template if rule hit. | Enum (Lookup) | Optional. |
+| Stop if criteria met | If true, halts further rule evaluation for this TC. | Boolean | Default False. |
+| Do not update pool | Rule updates Counters/Attributes but not the pool. | Boolean | Default False. |
+
+#### Transaction Code Linkage
+| Field Name | Description | Logic Type | Constraints / Rules |
+|---|---|---|---|
+| Transaction Code | TC that triggers this rule. | Enum (Lookup) | Required. |
+| Execution Sequence | Priority order of execution. | Integer | Required. Unique per Rule Type + TC combo. |
+
+#### Formula Setting (If Rule Type requires formula)
+| Field Name | Description | Logic Type | Constraints / Rules |
+|---|---|---|---|
+| Amount to Use (A) | Derived amount (from tx data or counter). | Enum | Required. |
+| Cap A not more than | Caps the input 'A'. | Decimal | Optional. |
+| Formula Result is rounded | Down, Nearest, Up. | Enum | Required. |
+| Award Limit (At Least) | Minimum guaranteed result. | Decimal | Optional. |
+| Award Limit (No More Than) | Max limit (can be tied to a Counter). | Decimal | Optional. |
+
+### Execution
+- An incoming transaction's TC is matched against Rules.
+- Rules linked to the TC are evaluated in Execution Sequence order.
+- If Rule Criteria (defined separately) pass, the Formula (defined separately) calculates the reward.
+- If "Stop if criteria met" is true, processing halts.
+
+## Exception Flow
+- N/A