Add CODE_OF_CONDUCT and PULL_REQUEST_TEMPLATE

- Add CODE_OF_CONDUCT.md based on Contributor Covenant 2.1
- Add .github/PULL_REQUEST_TEMPLATE.md with structured sections
- Link CODE_OF_CONDUCT in README.md and CONTRIBUTING.md

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,45 @@
+<!--
+Thanks for contributing to KoalaSync!
+
+Please read the CONTRIBUTING.md and CODE_OF_CONDUCT.md before submitting.
+By submitting this PR, you agree to abide by our code of conduct.
+
+Use conventional commits for the title: feat:, fix:, docs:, refactor:, chore:
+-->
+
+### Description
+
+<!-- What does this PR do and why? Link to relevant issue or motivation. -->
+
+Closes #
+
+### Type of Change
+
+- [ ] Bug fix (non-breaking change that fixes an issue)
+- [ ] New feature (non-breaking change that adds functionality)
+- [ ] Breaking change (fix or feature that alters existing behavior)
+- [ ] Refactoring (no functional changes)
+- [ ] Documentation update
+- [ ] Build, dependencies, or CI
+
+### How Has This Been Tested?
+
+<!-- Describe the tests you ran and the environments (browsers, OS, etc.) -->
+
+- [ ] Tested on Chrome
+- [ ] Tested on Firefox
+- [ ] `npm run lint` passes with zero errors and zero warnings
+- [ ] `node -c` passes on all modified `.js` files
+
+### Checklist
+
+- [ ] My code follows the project's style guidelines
+- [ ] I have performed a self-review of my code
+- [ ] I have added/updated tests if needed
+- [ ] I have updated documentation if needed (`docs/`, README, etc.)
+- [ ] Protocol changes: I ran `node scripts/build-extension.js` and updated relevant docs
+- [ ] No new warnings, secrets, or hardcoded credentials introduced
+
+### Additional Context
+
+<!-- Screenshots, migration notes, performance data, etc. -->