CI: Add PR validation workflow 💕

[Mie-Jonasson]

Description

This PR adds tests into the repo through a CI workflow that runs on every pull request.
The workflow builds the application and runs several static code analyses as well as API and UI tests.

Additionally, this PR takes care of some chore / cleanup tasks. A summary of the total changes:

• Naming all workflows with 'yaml' file extension rather than 'yml'
• Removal of legacy API python scripts that are not utilised in the repo and have many security issues.
• Linting of white space across the entire project
• Removal of one-time-migrations for Postgres database to ensure it runs on freshly initialised dbs as well
• Move all test-related code into "tests" root folder
• UI tests using selenium running on a separate docker container.
• Removal of hardcoded PWD in simulator script and some patches and improvements of the code and debug information.
• Makefile addition to always include environment vars from local .env file
• New make commands for spinning up postgres database
• New make commands for testing and linting, gathered in a single make command 'build-and-test' which is the only one that is called in the workflow.

Checklist:

• This PR represents one logical change to the codebase
• I have performed a self-review of my own code
• I have added tests that prove my fix is effective or that my feature works
• I updated log.md and/or README.md with relevant usage notes and choice documentation
• (If DB changes) I have tested the migration end-to-end locally and noted any pitfalls and expected downtime
• (If deployment/monitoring workflows changed) Required secrets and env vars are documented; workflow behaviour is as expected
• No secrets, API keys, or credentials are committed (only env examples or placeholders)

[sonarqubecloud]

Quality Gate failed

Failed conditions
4 Security Hotspots

See analysis details on SonarQube Cloud