Consolidate API documentation into single unified reference

- Created docs/API-COMPLETE-REFERENCE.md as single source of truth
- Removed redundant API documentation files:
  - docs/API-DOCUMENTATION.md
  - docs/DOCUMENTATION-SUMMARY.md
  - docs/README.md
  - unified-api/API-ENDPOINTS-ANALYSIS.md
  - unified-api/API-STANDARD-v1.0.md
- Updated main README.md with API documentation section
- Updated CHANGELOG.md with documentation consolidation details

README.md

@@ -44,7 +44,8 @@ igny8/
 │   ├── 03-FRONTEND-ARCHITECTURE.md
 │   ├── 04-BACKEND-IMPLEMENTATION.md
 │   ├── 05-AI-FRAMEWORK-IMPLEMENTATION.md
-│   └── 06-FUNCTIONAL-BUSINESS-LOGIC.md
+│   ├── 06-FUNCTIONAL-BUSINESS-LOGIC.md
+│   └── API-COMPLETE-REFERENCE.md  # Complete unified API documentation
 ├── CHANGELOG.md         # Version history and changes (only updated after user confirmation)
 └── docker-compose.app.yml
 ```
@@ -132,16 +133,62 @@ For complete installation guide, see [docs/01-TECH-STACK-AND-INFRASTRUCTURE.md](
 
 ---
 
-## 🔗 API Endpoints
+## 🔗 API Documentation
 
-- **Planner**: `/api/v1/planner/keywords/`, `/api/v1/planner/clusters/`, `/api/v1/planner/ideas/`
-- **Writer**: `/api/v1/writer/tasks/`, `/api/v1/writer/images/`
-- **System**: `/api/v1/system/settings/`
-- **Billing**: `/api/v1/billing/`
-- **Auth**: `/api/v1/auth/`
-- **Admin**: `/admin/`
+### Interactive Documentation
 
-See [docs/04-BACKEND-IMPLEMENTATION.md](docs/04-BACKEND-IMPLEMENTATION.md) for complete API reference.
+- **Swagger UI**: `https://api.igny8.com/api/docs/`
+- **ReDoc**: `https://api.igny8.com/api/redoc/`
+- **OpenAPI Schema**: `https://api.igny8.com/api/schema/`
+
+### API Complete Reference
+
+**[API Complete Reference](docs/API-COMPLETE-REFERENCE.md)** - Comprehensive unified API documentation (single source of truth)
+- Complete endpoint reference (100+ endpoints across all modules)
+- Authentication & authorization guide
+- Response format standards (unified format: `{success, data, message, errors, request_id}`)
+- Error handling
+- Rate limiting (scoped by operation type)
+- Pagination
+- Roles & permissions
+- Tenant/site/sector scoping
+- Integration examples (Python, JavaScript, cURL, PHP)
+- Testing & debugging
+- Change management
+
+### API Standard Features
+
+- ✅ **Unified Response Format** - Consistent JSON structure for all endpoints
+- ✅ **Layered Authorization** - Authentication → Tenant → Role → Site/Sector
+- ✅ **Centralized Error Handling** - All errors in unified format with request_id
+- ✅ **Scoped Rate Limiting** - Different limits per operation type (10-100/min)
+- ✅ **Tenant Isolation** - Account/site/sector scoping
+- ✅ **Request Tracking** - Unique request ID for debugging
+- ✅ **100% Implemented** - All endpoints use unified format
+
+### Quick API Example
+
+```bash
+# Login
+curl -X POST https://api.igny8.com/api/v1/auth/login/ \
+  -H "Content-Type: application/json" \
+  -d '{"email":"user@example.com","password":"password"}'
+
+# Get keywords (with token)
+curl -X GET https://api.igny8.com/api/v1/planner/keywords/ \
+  -H "Authorization: Bearer YOUR_TOKEN" \
+  -H "Content-Type: application/json"
+```
+
+### Additional API Guides
+
+- **[Authentication Guide](docs/AUTHENTICATION-GUIDE.md)** - Detailed JWT authentication guide
+- **[Error Codes Reference](docs/ERROR-CODES.md)** - Complete error code reference
+- **[Rate Limiting Guide](docs/RATE-LIMITING.md)** - Rate limiting and throttling details
+- **[Migration Guide](docs/MIGRATION-GUIDE.md)** - Migrating to API v1.0
+- **[WordPress Plugin Integration](docs/WORDPRESS-PLUGIN-INTEGRATION.md)** - WordPress integration guide
+
+For backend implementation details, see [docs/04-BACKEND-IMPLEMENTATION.md](docs/04-BACKEND-IMPLEMENTATION.md).
 
 ---
 
@@ -234,6 +281,7 @@ All documentation is consolidated in the `/docs/` folder.
 ### Finding Information
 
 **By Topic:**
+- **API Documentation**: [API-COMPLETE-REFERENCE.md](docs/API-COMPLETE-REFERENCE.md) - Complete unified API reference (single source of truth)
 - **Infrastructure & Deployment**: [01-TECH-STACK-AND-INFRASTRUCTURE.md](docs/01-TECH-STACK-AND-INFRASTRUCTURE.md)
 - **Application Architecture**: [02-APPLICATION-ARCHITECTURE.md](docs/02-APPLICATION-ARCHITECTURE.md)
 - **Frontend Development**: [03-FRONTEND-ARCHITECTURE.md](docs/03-FRONTEND-ARCHITECTURE.md)