Refactor architecture documentation and enhance security features

- Updated architecture constraints documentation to include detailed sections on technical, organizational, regulatory, environmental, and performance constraints.
- Created separate markdown files for each type of constraint for better organization and clarity.
- Revised the architecture scope section to provide a clearer overview of the system's key areas.
- Enhanced the solution strategy documentation with detailed explanations of the client-server architecture, technology choices, trade-offs, and future considerations.
- Added comprehensive descriptions of backend and frontend components, middleware, and utilities in the architecture documentation.
- Migrated UI, templates, and styling notes to a dedicated section for better structure.
- Updated requirements.txt to include missing dependencies.
- Refactored user authentication logic in the users.py and security.py files to improve code organization and maintainability, including the integration of OAuth2 password bearer token handling.

docs/architecture/02_constraints/02_05_performance_constraints.md

@@ -0,0 +1,14 @@
+---
+title: '02 — Performance Constraints'
+description: 'Performance constraints that affect architecture decisions.'
+status: draft
+---
+
+# Performance Constraints
+
+> e.g., response time requirements, scalability needs.
+
+Current performance constraints include:
+
+1. **Response Time Requirements**: The architecture must ensure that the system can respond to user requests within a specified time frame, which may impact design decisions related to caching, database queries, and API performance.
+2. **Scalability Needs**: The system should be able to handle increased load and user traffic without significant degradation in performance, necessitating a scalable architecture that can grow with demand.