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

docs/specs/customer_management/account.md

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+---
+title: "Account"
+type: OpenSpec
+status: Draft
+domain: Customer Management
+---
+
+# Account
+
+## Requirement Definition
+Manages customer account information, which is either sent from an external system to OLS or added by users manually via the OLS system.
+
+## Process Flow
+
+### Pre-Conditions
+- Users must have access rights in the "Account" module.
+- An account type must exist in OLS before an account of that type can be added.
+- The user must select a customer to access the Account tab.
+
+## Business Rules
+
+### Data Schema
+
+| Field Name | Description | Logic Type | Constraints / Rules |
+|---|---|---|---|
+| CIF Number | CIF number of selected customer. | String | Required. Read-only on creation. |
+| Product Account Level (PAL) | Product Account Level. | Enum (Lookup) | Required. |
+| Product Account Type (PAT) | Product Account Type. | Enum (Lookup) | Required. PAL + PAT = Account Type. |
+| Account Number | Product Account Number. | String (20) | Required. Combination of Account No + Account Type must be unique. |
+| Account Open Date | Open date of the account. | Date | Required. |
+| Account Indicator | Personal [P] or Corporate [C]. | Enum (Lookup) | Required. |
+| Account Block Code | Used to block transactions. | String (10) | Optional. |
+| Block Code Reason | Reason for blocking. | String (100) | Optional. |
+| Block Code Last Update Date | Date block was applied. | Date | Optional. |
+| Cycle | Statement cycle date. | Integer (2) | > 0 if provided. |
+| Account Status | Status of the account. | Enum (Lookup) | Required. |
+
+### Execution
+- Each account belongs to one Customer. The CIF number cannot be changed via this screen (requires CIF Merge batch).
+- Records managed by OLSACCT batch cannot typically be changed from the admin screen.
+- On Add: Rejected if Account No + Account Type already exists. Else, record added to PRODUCT_ACCOUNT and LOYALTY_ACCOUNT_PRODUCT created.
+- On Update: Must exist in OLS. Original record moved to history.
+- On Delete: Rejected if linked to an active Card record. Else, logical delete applied (moved to history).
+
+## Exception Flow
+- Input validation failures stop the action.