Fixes issues listed & UI improvements.

[SmokeHound]

This pull request focuses on improving the user interface and user experience of the SMS Backup Reader app, with significant enhancements to styling, usability, and performance. The most important changes include a major UI/UX refresh across multiple components, improved handling of large message backups to prevent UI freezing, and several bug fixes and minor improvements.

UI/UX Improvements:

• Major restyling and layout improvements for the app, including new styles for app headers, footers, buttons, and empty states (src/app/app.component.css, src/app/main/main.component.css, src/app/settings/settings.component.css, src/app/contact-list/contact-list.component.css, src/app/message-list/message-list.component.css, src/app/sms-loader/sms-loader.component.css, src/app/vcf-loader/vcf-loader.component.css) [1] [2] [3] [4] [5] [6]
• Updated HTML templates for a more modern and user-friendly experience, including improved empty state messaging, enhanced contact and message list layouts, and better file upload buttons with icons (src/app/main/main.component.html, src/app/settings/settings.component.html, src/app/contact-list/contact-list.component.html, src/app/message-list/message-list.component.html, src/app/sms-loader/sms-loader.component.html, src/app/vcf-loader/vcf-loader.component.html) [1] [2] [3] [4] [5] [6]

Performance and Data Handling:

• Improved performance when loading large message backups by processing messages in chunks asynchronously, preventing UI freezing and ensuring smoother experience for large datasets (src/app/sms-store.service.ts) [1] [2] [3]
• Updated the logic for changing country codes to ensure contact names are filled only after both messages and contacts are loaded (src/app/country-select/country-select.component.ts)
• Fixed incorrect country code for Indonesia in the country select list (src/app/country-select/country-select.component.ts)

Minor Fixes and Improvements:

• Improved placeholder and help text for better clarity (src/app/main/main.component.ts)
• Updated styles and markup for the country select dropdown for a more consistent look (src/app/country-select/country-select.component.css, src/app/country-select/country-select.component.html) [1] [2]
• Updated README to remove outdated warnings about performance and UX, reflecting improvements made in this PR (README.md)

Bug Fixes:

• Fixed promise resolution and message loaded broadcasting logic when changing country code and loading contacts/messages (src/app/sms-store.service.ts, src/app/vcf-store.service.ts) [1] [2]

These changes collectively make the app more visually appealing, responsive, and user-friendly, especially for users with large SMS backups.