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docs/DATABASE.md

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+# Database Documentation
+
+MiauInv utilizes an embedded SQLite database instance for persistent data storage. Foreign key constraints are strictly enforced at the database level.
+
+## Configuration
+To ensure data integrity, every database connection initialization explicitly executes the following command before handling queries:
+```sql
+PRAGMA foreign_keys = ON;
+```
+
+---
+
+## Schema Architecture
+
+### Entity-Relationship Summary
+
+The database consists of primary entity tables (`users`, `items`, `locations`, `projects`) and relational junction tables (`stock`, `project_items`, `refresh_tokens`) designed to track stock distribution and access sessions.
+
+```
+[users] <--- (1:N) ---> [refresh_tokens]
+[items] <--- (1:N) ---> [stock] <--- (N:1) ---> [locations]
+[items] <--- (1:N) ---> [project_items] <--- (N:1) ---> [projects]
+```
+
+---
+
+## Table Definitions
+
+### 1. users
+
+Stores user credentials and operational roles within the system.
+
+* **id (TEXT, PK):** Unique UUID
+* **username (TEXT, Unique):** Unique account identifier.
+* **password (TEXT):** Hashed user password.
+* **role (TEXT):** Access control flag (e.g., admin, user).
+
+### 2. refresh_tokens
+
+Tracks valid extended sessions linked to specific user accounts.
+
+* **id (TEXT, PK):** Unique identifier.
+* **user_id (TEXT, FK):** References `users(id)`.
+* **token_hash (TEXT):** Cryptographic hash of the active refresh token.
+* **expires_at (INTEGER):** Unix timestamp indicating token expiration.
+* **created_at (INTEGER):** Unix timestamp indicating session creation.
+* **revoked (INTEGER):** Boolean flag (0 or 1) indicating if the session was manually invalidated.
+* **device_info (TEXT, Optional):** Client metadata for auditing.
+
+### 3. items
+
+Represents individual tracked assets.
+
+* **id (INTEGER, PK, Autoincrement):** Primary key.
+* **name (TEXT):** Asset designation.
+* **category (TEXT, Optional):** Grouping classification.
+* **description (TEXT, Optional):** Detailed asset context.
+* **total_quantity (INTEGER):** Absolute global stock baseline counter.
+
+### 4. locations
+
+Defines logical or physical facilities.
+
+* **id (INTEGER, PK, Autoincrement):** Primary key.
+* **name (TEXT, Unique):** Unique facility naming constraint.
+
+### 5. projects
+
+Defines distinct tasks or allocation targets.
+
+* **id (INTEGER, PK, Autoincrement):** Primary key.
+* **name (TEXT, Unique):** Unique operational tracking name.
+* **description (TEXT, Optional):** Scope description.
+
+### 6. stock
+
+Junction table mapping physical asset distributions across facilities.
+
+* **id (INTEGER, PK, Autoincrement):** Primary key.
+* **item_id (INTEGER, FK):** References `items(id)`.
+* **location_id (INTEGER, FK):** References `locations(id)`.
+* **quantity (INTEGER):** Specific quantity present at this location node.
+
+### 7. project_items
+
+Junction table tracking asset assignments dedicated to specific ongoing project environments.
+
+* **id (INTEGER, PK, Autoincrement):** Primary key.
+* **item_id (INTEGER, FK):** References `items(id)`.
+* **project_id (INTEGER, FK):** References `projects(id)`.
+* **quantity (INTEGER):** Quantity allocated to this project context.
+---
+
+## Data Integrity Constraints
+
+* **Foreign Keys:** Because standard `ON DELETE` cascades are not defined explicitly in the schema rules, SQLite blocks parent deletion actions if dependent rows exist in `stock` or `project_items`. You must clear out stock allocations and project associations manually before deleting an item, location, or project.
+* **Uniqueness:** String uniqueness constraints protect against duplicate namespace registration on `users(username)`, `locations(name)`, and `projects(name)`.