Remove devcontainer setup and update workflows to use master branch

[Copilot]

This PR removes the devcontainer setup from the repository and updates the GitHub Actions workflow to trigger on the master branch for both pull requests and merges.

Changes

Removed Devcontainer Configuration

The .devcontainer directory and all its contents have been removed:

• Dockerfile - Dev container Docker image configuration
• devcontainer.json - VS Code devcontainer settings
• docker-compose.yml - Docker Compose setup for PostgreSQL database
• README.md - Devcontainer documentation

The devcontainer setup is no longer needed as developers can use local development environments or other containerization approaches documented elsewhere.

Updated GitHub Actions Workflow

The .github/workflows/tests.yml workflow has been updated to align with the repository's default branch:

Before:

on:
  push:
    branches: [ main, develop ]
  pull_request:
    branches: [ main, develop ]

After:

on:
  push:
    branches: [ master ]
  pull_request:
    branches: [ master ]

This ensures all Rust test workflows (unit tests, integration tests, and edge case tests) run correctly for:

• Pull requests targeting the master branch
• Direct pushes to the master branch

All three test jobs remain unchanged and will continue to run:

1. Unit Tests - Runs unit tests, rustfmt formatting checks, and clippy linting
2. Integration Tests - Runs integration tests with PostgreSQL
3. Edge Case Tests - Runs edge case tests with PostgreSQL

Verification

• ✅ CodeQL security analysis passed with no vulnerabilities detected
• ✅ Workflow configuration validated against repository default branch
• ✅ All test jobs preserved and operational

Original prompt

Remove the devcontainer setup and ensure all rust test workflows are running for pull requests and mergesl into master.

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