Automate releases from PR titles and clean up CI workflows.

Add release and PR title checks, shared CI scripts, Gitea PR template, and align pyproject.toml to v0.3.1.

Co-authored-by: Cursor <[email protected]>

.gitea/PULL_REQUEST_TEMPLATE.md

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+## Version bump
+
+If this PR changes files under `python_repositories/`, the **title must** start with one of:
+
+- `[patch]` or `[fix]` — bug fix (0.3.1 → 0.3.2)
+- `[minor]` or `[feat]` — new feature (0.3.1 → 0.4.0)
+- `[major]` or `[breaking]` — breaking change (0.3.1 → 1.0.0)
+
+Docs-, CI-, or test-only PRs do not need a prefix.
+
+**Example title:** `[minor] Add streaming support to RedisAdapter`
+
+## Summary
+
+<!-- What changed and why -->
+
+## Test plan
+
+- [ ] Integration tests pass locally