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/05_blocks/05_02_backend_components.md

@@ -0,0 +1,13 @@
+---
+title: '05 — Backend Components'
+description: 'Description of the backend components of the CalMiner application.'
+status: draft
+---
+
+- **FastAPI application** (`main.py`): entry point that configures routers, middleware, and startup/shutdown events.
+- **Routers** (`routes/`): modular route handlers for scenarios, parameters, costs, consumption, production, equipment, maintenance, simulations, and reporting. Each router defines RESTful endpoints, request/response schemas, and orchestrates service calls.
+  - leveraging a shared dependency module (`routes/dependencies.get_db`) for SQLAlchemy session management.
+- **Models** (`models/`): SQLAlchemy ORM models representing database tables and relationships, encapsulating domain entities like Scenario, CapEx, OpEx, Consumption, ProductionOutput, Equipment, Maintenance, and SimulationResult.
+- **Services** (`services/`): business logic layer that processes data, performs calculations, and interacts with models. Key services include reporting calculations and Monte Carlo simulation scaffolding.
+  - `services/settings.py`: manages application settings backed by the `application_setting` table, including CSS variable defaults, persistence, and environment-driven overrides that surface in both the API and UI.
+- **Database** (`config/database.py`): sets up the SQLAlchemy engine and session management for PostgreSQL interactions.