chore: add GitHub issue templates, PR template, and contributor labels

[SharanyoBanerjee]

Problem

The project asks contributors to use GitHub issues before contributing, but there are no issue templates or PR template yet. As the repo opens up, maintainers will get more consistent contributions if GitHub guides the shape of reports and PRs.

Suggested fix

Add:

• .github/ISSUE_TEMPLATE/bug_report.yml
• .github/ISSUE_TEMPLATE/feature_request.yml
• .github/ISSUE_TEMPLATE/docs.yml
• .github/pull_request_template.md
• starter labels such as area:web, area:api, area:ai-service, area:docs, priority:p0, priority:p1, priority:p2, good first issue, and help wanted

Acceptance criteria

• New issues ask for expected/actual behavior, setup context, and affected area.
• New PRs ask for summary, screenshots if UI, test evidence, and linked issue.
• Area and priority labels exist or are documented for maintainers to create.

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