chore: add bug report template and config

[ABEEGOLD]

Closes #211

Summary

This PR rounds out the issue-template set by adding a structured bug report form. This resolves inconsistent triage quality by ensuring bug reports no longer start as a blank freeform box, while routing security-related reports properly to our vulnerability disclosure process.

Changes Made

• Added .github/ISSUE_TEMPLATE/bug_report.yml: Created a structured issue form with dedicated fields for affected module (engine-core, engine-bridge, dashboard), expected/actual behavior, and reproduction steps.
• Added .github/ISSUE_TEMPLATE/config.yml: Disabled blank issues to enforce template usage and added a contact link pointing users looking to report security vulnerabilities directly to the SECURITY.md process instead of the public tracker.

Testing Performed

• Unit tests pass (cargo test / npm test)
• Integration tests pass
• Manual smoke test performed (Verified YAML syntax and structure for issue forms)

Checklist

• Branch follows naming convention (feat/, fix/, chore/, etc.)
• Closes #211 reference is present above (linking this PR to the issue)
• Code follows the project's style and conventions
• New or updated tests cover the changes
• Documentation updated if behaviour changed
• No secrets, credentials, or sensitive data committed
• PR is scoped to a single concern (one issue per PR)

[N-thnI]

CI green, assignee-verified against GrantFox campaign assignment.