chore(repo): add PR and bug-report templates

[Adiz4415]

Summary

Adds a default PR description template at .github/pull_request_template.md AND a bug-report issue template at .github/ISSUE_TEMPLATE/bug_report.md, so future contributors and bug reporters have consistent structures for describing changes, test plans, reproduction steps, severity, and breaking changes.

Previously the repo only had a single generic .github/ISSUE_TEMPLATE/feature_request.md and no PR template.

Changes

• Adds .github/pull_request_template.md with sections: Summary, Related Issues, Changes, Test Plan / Verification, Screenshots / Recordings, Checklist, Breaking Changes, Notes for Reviewers. Title guidance reflects the project's actual commit style (feat(frontend): …, fix: …, chore: …, docs: …); the Checkset line notes that pnpm changeset runs at the repo root with auto‑bucketing.
• Adds .github/ISSUE_TEMPLATE/bug_report.md with sections: Summary, Steps to Reproduce, Expected/Actual Behavior, Environment (wallet/network/branch/SHA/browser/OS), Logs / Artifacts (with a secrets‑redaction reminder), Related Issues/PRs, Severity (🟢/🟡/🟠/🔴), Possible Cause (optional), Reproduction Checklist.
• Style of both files consistent with the existing feature_request.md in the same directory.

Test Plan / Verification

• Both files render correctly when previewing issue/PR descriptions on GitHub.
• The new templates are auto-picked-up by GitHub’s issue/PR chooser.
• No code, schema, environment, or production behavior is touched — this is a documentation-only change with no runtime impact.

Checklist

• Conventional Commits commit messages (chore(repo): …)
• No user-facing behavior changed — no changeset needed
• No code changes — no tests required
• No new warnings from pnpm lint / cargo clippy
• No breaking changes

Notes for Reviewers

The two templates are committed as separate logical commits on the same branch (chore/add-pull-request-template, base = main). Both are content-only additions; deletion of either would be safe and trivial to revert.

[3m1n3nc3]

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