test: add XCTest foundation and CI coverage

[hnduy910]

Summary

• Add a real NetFlowTests XCTest target covering plan-cycle boundaries, forecasts, usage tracking, midnight aggregation, persistence, backup, and CSV output.
• Harden monthly and yearly reset calculations, manual usage handling for closed cycles, and byte-counter overflow behavior.
• Add CI test execution, CI-gated release automation, CodeQL, Dependabot, CODEOWNERS, security routing, and source hygiene.
• Remove tracked IPA binaries and improve README and contributor guidance.

Validation

• bash Tools/check_project.sh — passed.
• Swift parse and production Swift module compilation — passed.
• Workflow YAML parsing and git diff --check — passed.
• Local XCTest execution remains unverified because this Mac session has no available iOS Simulator runtime; GitHub Actions is configured to run the suite on macOS 15 with iPhone 16.

Review notes

Please review the generated Xcode project, release workflow trigger, and the data-plan boundary tests before merging.

[github-advanced-security]

You are seeing this message because GitHub Code Scanning has recently been set up for this repository, or this pull request contains the workflow file for the Code Scanning tool.

What Enabling Code Scanning Means:

• The 'Security' tab will display more code scanning analysis results (e.g., for the default branch).
• Depending on your configuration and choice of analysis tool, future pull requests will be annotated with code scanning analysis results.
• You will be able to see the analysis results for the pull request's branch on this overview once the scans have completed and the checks have passed.

For more information about GitHub Code Scanning, check out the documentation.