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

docs/specs/reward_campaign/campaign_rule_formula.md

@@ -0,0 +1,27 @@
+---
+title: "Campaign Rule Formula"
+type: OpenSpec
+status: Draft
+domain: Reward Campaign Management
+---
+
+# Campaign Rule Formula
+
+## Requirement Definition
+Configures the mathematical formula used to calculate the reward, redemption value, or counter increment for a given Rule.
+
+## Process Flow
+
+### Pre-Conditions
+- Rule must be created.
+
+## Business Rules
+
+### Execution
+- Formulas act on the "Amount to Use (A)" defined in the Rule Header.
+- Support mathematical operations (e.g., A * 0.05, A + 10).
+- Formulas can be assigned to different tiers based on criteria.
+- Formulas can be used to update Pool Balances, or simply update a Counter / Attribute without impacting a Pool.
+
+## Exception Flow
+- N/A