Add colour themes, improve translations & internationalization

[hessius]

This pull request updates the Swedish localization in aura/translations.h to improve translation accuracy and correct several spelling errors. The changes enhance the clarity and correctness of the Swedish user interface.

Localization improvements:

• Added translations for "am" and "pm" as "fm" and "em", and corrected several Swedish terms and spellings (e.g., "Återställ Wi-Fi", "Ändra plats", "åtkomstpunkten") in strings_sv for better language accuracy.
• Improved phrasing and corrected spelling in confirmation dialogs and labels (e.g., "Är du säker på att du vill...", "Du måste återansluta...", "Språk:", weekday abbreviations, "Dimma nattetid") in strings_sv.

[hessius]

This pull request introduces two main improvements: it adds themes - a customizable color scheme system to the UI, and expands internationalization support by updating translation strings and switching to internationalized fonts. The color scheme system allows users to select from multiple color themes, with full translation support for the new option in all supported languages. Additionally, the Montserrat font is replaced with a version that provides comprehensive UTF-8 support for international characters as I discovered that the previous implementation was missing characters needed e.g. to display names of days in Swedish correctly.

UI Theming and Color Scheme Support

• Added a new ColorScheme enum and ColorSchemeData struct to define multiple UI color themes, including blue, red, yellow, orange, white, black, green, and pink. Helper functions (get_current_colors, apply_background_colors, apply_box_colors) were added to apply the selected scheme to UI elements. The color scheme is persisted in preferences and loaded at startup. ([[1]](https://github.com/Surrey-Homeware/Aura/pull/23/files#diff-3cb021f6e9b5beca373674fc7baaa08e514c1de0f957552dff93a74d396405c5L33-R120), [[2]](https://github.com/Surrey-Homeware/Aura/pull/23/files#diff-3cb021f6e9b5beca373674fc7baaa08e514c1de0f957552dff93a74d396405c5R411))
• Added a color scheme dropdown (color_scheme_dropdown) to the settings window, allowing users to select their preferred UI theme. ([[1]](https://github.com/Surrey-Homeware/Aura/pull/23/files#diff-3cb021f6e9b5beca373674fc7baaa08e514c1de0f957552dff93a74d396405c5R172), [[2]](https://github.com/Surrey-Homeware/Aura/pull/23/files#diff-3cb021f6e9b5beca373674fc7baaa08e514c1de0f957552dff93a74d396405c5R234-R236))

Internationalization Enhancements

• Replaced Montserrat Latin fonts with internationalized Montserrat fonts for comprehensive UTF-8 character support, ensuring proper rendering of all supported languages. ([aura/weather.inoL33-R120](https://github.com/Surrey-Homeware/Aura/pull/23/files#diff-3cb021f6e9b5beca373674fc7baaa08e514c1de0f957552dff93a74d396405c5L33-R120))
• Updated the LocalizedStrings struct and all language translations to include a new label for the color scheme selector. All supported languages now have a translated string for "Color scheme:". ([[1]](https://github.com/Surrey-Homeware/Aura/pull/23/files#diff-087ae745ad1a53b9c431716a2d15ccec8255feeb32afaf862f95f4b3f6501a0dR36), [[2]](https://github.com/Surrey-Homeware/Aura/pull/23/files#diff-087ae745ad1a53b9c431716a2d15ccec8255feeb32afaf862f95f4b3f6501a0dR68), [[3]](https://github.com/Surrey-Homeware/Aura/pull/23/files#diff-087ae745ad1a53b9c431716a2d15ccec8255feeb32afaf862f95f4b3f6501a0dR100), [[4]](https://github.com/Surrey-Homeware/Aura/pull/23/files#diff-087ae745ad1a53b9c431716a2d15ccec8255feeb32afaf862f95f4b3f6501a0dR134), [[5]](https://github.com/Surrey-Homeware/Aura/pull/23/files#diff-087ae745ad1a53b9c431716a2d15ccec8255feeb32afaf862f95f4b3f6501a0dR168), [[6]](https://github.com/Surrey-Homeware/Aura/pull/23/files#diff-087ae745ad1a53b9c431716a2d15ccec8255feeb32afaf862f95f4b3f6501a0dR199-R215), [[7]](https://github.com/Surrey-Homeware/Aura/pull/23/files#diff-087ae745ad1a53b9c431716a2d15ccec8255feeb32afaf862f95f4b3f6501a0dL218-R236), [[8]](https://github.com/Surrey-Homeware/Aura/pull/23/files#diff-087ae745ad1a53b9c431716a2d15ccec8255feeb32afaf862f95f4b3f6501a0dR264))

Cleanup

• Removed the now-obsolete lv_font_montserrat_latin_XX.c files, as the new internationalized font replaces it. ([aura/lv_font_montserrat_latin_12.cL1-L366](https://github.com/Surrey-Homeware/Aura/pull/23/files#diff-a2d96f66cd50cdd12e4ec22027af38d88f97c37aca7e08e4207ceb525730e2aeL1-L366))

UI Consistency

• Updated all relevant UI code to use the new color scheme and font selection logic, including the Wi-Fi splash screen and settings. ([aura/weather.inoL389-R455](https://github.com/Surrey-Homeware/Aura/pull/23/files#diff-3cb021f6e9b5beca373674fc7baaa08e514c1de0f957552dff93a74d396405c5L389-R455))

These changes collectively improve the user experience by making the UI more visually customizable and accessible to a broader range of languages and scripts.

[hessius]

This pull request now also introduces multi-language support for color scheme selection.