chore: GitHub issue templates for template requests + feature requests

[ajianaz]

Source: user-needs research — there is no official channel for users to request templates/features yet.

Proposed design:

• .github/ISSUE_TEMPLATE/template_request.yml: form (template name, use case, size, visual reference/link, sample content).
• .github/ISSUE_TEMPLATE/feature_request.yml: form (problem, proposed solution, alternatives).
• .github/ISSUE_TEMPLATE/config.yml with contact links (Discord).

Acceptance:

• /issues/new?template=... shows the form; automatic labels (template-request, enhancement).

Effort: S. Priority #7 (cheapest user research).