Add GitHub issue templates: bug report, feature request

[zeevdr]

Description

Add structured issue templates so external users provide the info needed for triage. Applies to all decree repos.

Acceptance criteria

• .github/ISSUE_TEMPLATE/bug_report.yml — version, steps to reproduce, expected vs actual, environment
• .github/ISSUE_TEMPLATE/feature_request.yml — use case, proposed solution, alternatives considered
• .github/ISSUE_TEMPLATE/config.yml — disable blank issues, point to Discussions for questions
• Replicate templates to decree-python, decree-typescript, decree-ui (or use org-level .github repo after org migration)

Notes

• Use YAML form templates (not markdown) for structured input
• Include SDK version, Go/Python/Node version, and server version fields in bug template
• config.yml should redirect "How do I...?" questions to GitHub Discussions