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

docs/specs/reward_campaign/item_redemption_rule.md

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+---
+title: "Item Redemption Rule"
+type: OpenSpec
+status: Draft
+domain: Reward Campaign Management
+---
+
+# Item Redemption Rule
+
+## Requirement Definition
+Evaluates item redemption transactions (e.g. redeeming an eVoucher or physical item from a catalog).
+
+## Process Flow
+
+### Pre-Conditions
+- Users must have access rights.
+
+## Business Rules
+
+### Data Schema
+
+#### General Information
+| Field Name | Description | Logic Type | Constraints / Rules |
+|---|---|---|---|
+| Rule Type | Item Redemption (ITRD). | Enum | Required. |
+| Message Template ID | SMS/Email template if rule hit. | Enum (Lookup) | Optional. |
+| Transaction Code | TC used to post the redemption. | Enum (Lookup) | Required. |
+
+### Execution
+- Same criteria evaluation approach as Award rules.
+- There is NO reward pool, formula, or contributor attached to this rule type.
+- The redemption pool to deduct from is configured separately in the Item Price configuration.
+- To post an item redemption, the transaction must pass the validation criteria of the Item Redemption Rule linked to the redemption TC.
+
+## Exception Flow
+- Criteria failure blocks the item redemption transaction.