Add comprehensive documentation and unit tests

Documentation:
- Add detailed README files for all services (auth, character, database, launcher, packet, utils, world)
- Create API documentation for the database service with detailed endpoint specifications
- Document database schema and relationships
- Add service architecture overviews and configuration instructions

Unit Tests:
- Implement comprehensive test suite for database repositories (user, character, session)
- Add gRPC service tests for database interactions
- Create tests for packet service components (bufferpool, connection, packets)
- Add utility service tests (health check, logging, load balancer, redis cache, service discovery)
- Implement auth service user tests
- Add character service tests

Code Structure:
- Reorganize test files into a more consistent structure
- Create a dedicated tests crate for integration testing
- Add test helpers and mock implementations for easier testing

database-service/SCHEMA.md

@@ -0,0 +1,129 @@
+# Database Schema
+
+This document describes the database schema used by the Database Service.
+
+## Tables
+
+### User
+
+Stores user account information.
+
+| Column     | Type                | Description                       |
+|------------|---------------------|-----------------------------------|
+| id         | INTEGER             | Primary key                       |
+| name       | VARCHAR             | Username                          |
+| email      | VARCHAR             | Email address                     |
+| role       | VARCHAR             | User role (e.g., admin, user)     |
+| createdAt  | TIMESTAMP           | Account creation timestamp        |
+| updatedAt  | TIMESTAMP           | Last update timestamp             |
+
+### Character
+
+Stores character information.
+
+| Column     | Type                | Description                       |
+|------------|---------------------|-----------------------------------|
+| id         | INTEGER             | Primary key                       |
+| userId     | INTEGER             | Foreign key to User.id            |
+| name       | VARCHAR             | Character name                    |
+| money      | BIGINT              | Character's currency              |
+| inventory  | JSONB               | Serialized inventory data         |
+| stats      | JSONB               | Character statistics              |
+| skills     | JSONB               | Character skills                  |
+| looks      | JSONB               | Character appearance              |
+| position   | JSONB               | Character position in world       |
+| createdAt  | TIMESTAMP           | Character creation timestamp      |
+| updatedAt  | TIMESTAMP           | Last update timestamp             |
+| deletedAt  | TIMESTAMP           | Deletion timestamp (if deleted)   |
+| isActive   | BOOLEAN             | Whether character is active       |
+
+### Session
+
+Stores session information.
+
+| Column     | Type                | Description                       |
+|------------|---------------------|-----------------------------------|
+| id         | VARCHAR             | Session ID (primary key)          |
+| userId     | INTEGER             | Foreign key to User.id            |
+| createdAt  | TIMESTAMP           | Session creation timestamp        |
+| expiresAt  | TIMESTAMP           | Session expiration timestamp      |
+
+## JSON Structures
+
+### Inventory
+
+```json
+{
+  "items": [
+    {
+      "id": 1,
+      "itemId": 1001,
+      "count": 5,
+      "slot": 0
+    }
+  ],
+  "capacity": 100
+}
+```
+
+### Stats
+
+```json
+{
+  "strength": 10,
+  "dexterity": 10,
+  "intelligence": 10,
+  "vitality": 10,
+  "hp": 100,
+  "mp": 100,
+  "level": 1,
+  "experience": 0
+}
+```
+
+### Skills
+
+```json
+{
+  "skills": [
+    {
+      "id": 1,
+      "level": 1,
+      "cooldown": 0
+    }
+  ]
+}
+```
+
+### Looks
+
+```json
+{
+  "race": 1,
+  "gender": 0,
+  "hair": 1,
+  "face": 1,
+  "height": 180,
+  "skinColor": "#F5DEB3"
+}
+```
+
+### Position
+
+```json
+{
+  "mapId": 1,
+  "x": 100.0,
+  "y": 100.0,
+  "z": 0.0,
+  "direction": 0
+}
+```
+
+## Indexes
+
+- `user_name_idx`: Index on User.name for fast username lookups
+- `user_email_idx`: Index on User.email for fast email lookups
+- `character_user_id_idx`: Index on Character.userId for fast character list retrieval
+- `character_name_idx`: Index on Character.name for name uniqueness checks
+- `session_user_id_idx`: Index on Session.userId for user session lookups