UI and Save Management improvements

[JaviLendi]

This pull request introduces several enhancements and fixes across the VLM application, focusing on state management, user interface improvements, and internationalization support. The most notable changes are the addition of a modern language selector with Google Translate integration, improved VLM state saving and loading mechanisms, and significant CSS updates for better usability and accessibility.

UI Enhancements:

• Updated CSS to support the new language selector, including responsive styles, button states, and flag icons for supported languages. (src/vlm/static/css/style.css)

VLM State Management Improvements:

• Improved VLM state saving to include timestamped filenames for computed results, ensuring unique state files and better traceability. (src/vlm/app.py)
• Refactored the VLM state loading endpoint to accept uploaded state files, update session data, and return relevant aerodynamic parameters after loading. (src/vlm/app.py)

Styling and Usability Updates:

• Refined button styles for consistency and accessibility, including hover effects, padding, and font size adjustments. (src/vlm/static/css/style.css) [1] [2]
• Added new CSS variables and styles for info pop-ups, settings panels, and configuration descriptions, enhancing the application's look and feel. (src/vlm/static/css/style.css) [1] [2] [3]

Configuration and Data Updates:

• Updated cached plane variables and added a new airfoil configuration file for improved data management and reproducibility. (src/vlm/data/cache_plane_variables.txt, src/vlm/data/saved_configs/airfoil_hgj.json) [1] [2]

Miscellaneous:

• Minor code cleanup and import additions in src/vlm/app.py.