[fleizean]

Summary

Adds a pull request template and tightens the comment rule in CONTRIBUTING.md.

Why

Pull request descriptions had no fixed shape, and the code carried comments that described the task or the package behind a change instead of the code itself.

Changes

• .github/pull_request_template.md: Summary, Why, Changes, Notes for reviewers, and a checklist built from the rules in CONTRIBUTING.md.
• CONTRIBUTING.md: pull requests use the template, in English. Comments are kept to a minimum and never name the task or package that prompted a change; that context goes in the pull request description.

Notes for reviewers

None. Documentation only.

Checklist

• The pull request targets develop and is about one thing
• Commit messages follow Conventional Commits (feat(scope): ..., fix(scope): ...)
• CI is green (backend tests, frontend build and tests, dependency gate)
• Schema changes are EF Core migrations generated by the tool, not hand-edited
• A changed backend DTO has its TypeScript twin updated in src/frontend/src/app/core/models
• New dependencies are justified and their lock files are updated in the same commit
• No secrets, tokens or personal data in code, logs or this description
• Code comments are kept to a minimum; the reasoning lives in this description