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_01_technical_constraints.md

@@ -0,0 +1,16 @@
+---
+title: '02 — Technical Constraints'
+description: 'Technical constraints that affect architecture decisions.'
+status: draft
+---
+
+# Technical Constraints
+
+> e.g., choice of FastAPI, PostgreSQL, SQLAlchemy, Chart.js, Jinja2 templates.
+
+The architecture of CalMiner is influenced by several technical constraints that shape its design and implementation:
+
+1. **Framework Selection**: The choice of FastAPI as the web framework imposes constraints on how the application handles requests, routing, and middleware. FastAPI's asynchronous capabilities must be leveraged appropriately to ensure optimal performance.
+2. **Database Technology**: The use of PostgreSQL as the primary database system dictates the data modeling, querying capabilities, and transaction management strategies. SQLAlchemy ORM is used for database interactions, which requires adherence to its conventions and limitations.
+3. **Frontend Technologies**: The decision to use Jinja2 for server-side templating and Chart.js for data visualization influences the structure of the frontend code and the way dynamic content is rendered.
+4. **Simulation Logic**: The Monte Carlo simulation logic must be designed to efficiently handle large datasets and perform computations within the constraints of the chosen programming language (Python) and its libraries.