Modernize styling structure and fix component imports

[nikomakela]

LIIKUNTA-768

Several architectural improvements and necessary fixes related to styling, component imports, and exports.

The changes aim to clean up the codebase, leverage modern SCSS features, and ensure compatibility with build environments like Turbopack.

1. Removes unnecessary, unused, or redundant Sass files from the application directory, contributing to a cleaner codebase.
2. Refactors style imports to utilize the Sass @forward rule, allowing us to better manage and share variables, mixins, and configuration across different modules.
3. Moves the application's global CSS import to the top-level App component. This resolves warnings (e.g., from Turbopack) which enforce that global stylesheets must only be imported in the main App component to prevent conflicts and ensure predictable styling.
4. Corrects the export statement for the BaseApp Fallback component, ensuring it is properly available for consumption throughout the application.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[terovirtanen]

FEDERATION-ROUTER branch is deployed to platta: https://events-graphql-federation-hobbies-pr920.dev.hel.ninja 🚀🚀🚀

[terovirtanen]

FEDERATION-ROUTER branch is deployed to platta: https://events-graphql-federation-events-pr920.dev.hel.ninja 🚀🚀🚀

[terovirtanen]

FEDERATION-ROUTER branch is deployed to platta: https://events-graphql-federation-sports-pr920.dev.hel.ninja 🚀🚀🚀

[terovirtanen]

VENUE-GRAPHQL-PROXY branch is deployed to platta: https://venue-graphql-proxy-pr920.dev.hel.ninja 🚀🚀🚀

[terovirtanen]

EVENTS-GRAPHQL-PROXY branch is deployed to platta: https://events-graphql-proxy-pr920.dev.hel.ninja 🚀🚀🚀

[terovirtanen]

HARRASTUKSET-UI branch is deployed to platta: https://harrastukset-pr920.dev.hel.ninja 🚀🚀🚀

[terovirtanen]

TAPAHTUMAT-UI branch is deployed to platta: https://tapahtumat-pr920.dev.hel.ninja 🚀🚀🚀

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[terovirtanen]

LIIKUNTA-UI branch is deployed to platta: https://liikunta-pr920.dev.hel.ninja 🚀🚀🚀

[terovirtanen]

TestCafe result is failed for https://harrastukset-pr920.dev.hel.ninja 😿💢💥💥

[terovirtanen]

TestCafe result is failed for https://tapahtumat-pr920.dev.hel.ninja 😿💢💥💥

[terovirtanen]

TestCafe result is failed for https://liikunta-pr920.dev.hel.ninja 😿💢💥💥

[karisal-anders]

One refactoring/cleaning that came to mind is that the SCSS files that only forward another SCSS file aren't really necessary anymore. They imports that use them could be changed to use the forwarded files directly. Something to consider, not required for merging.