feat(github): accept issues on GitHub and auto-forward to Gitea

GitHub mirror previously redirected issue reporters to Gitea, which
requires login. Now GitHub Issues are accepted directly via form
templates (bug report + feature request) and a workflow forwards
new issues to Gitea with label mapping and provenance header.

.github/ISSUE_TEMPLATE/feature_request.yml

@@ -0,0 +1,20 @@
+name: Feature Request
+description: Suggest a new feature or enhancement
+labels:
+  - feature
+body:
+  - type: textarea
+    id: problem
+    attributes:
+      label: Problem
+      description: What's frustrating or missing?
+      placeholder: I find myself always needing to ...
+    validations:
+      required: true
+  - type: textarea
+    id: solution
+    attributes:
+      label: Proposed solution
+      description: How would you like this to work?
+    validations:
+      required: false