docs: add feature request + improvement issue templates, auto-assign new issues (#21)

- Add 2-feature_request.md and 3-improvement.md templates (chooser now
  lists Bug report, Feature request, Improvement in order)
- Improve bug report template: cross-template pointer, Linux log hint,
  Related issues/PRs section, demo-DB reproduction hint
- Auto-assign every newly opened issue to the repo owner:
  assignees in template front matter + a workflows/auto-assign.yml
  (covers issues opened without a template)
- Add ISSUE_TEMPLATE/config.yml with Roadmap/README contact links
- Update README Contributing section

.github/workflows/auto-assign.yml

@@ -0,0 +1,25 @@
+name: Auto-assign new issues
+
+# Assigns every newly opened issue to the repository owner so nothing
+# lands in the inbox untriaged. The `issues` event only fires in the base
+# repository (not forks) and this job never checks out code — it only
+# talks to the GitHub API, so there is no fork/pwn-request exposure.
+
+on:
+  issues:
+    types: [opened]
+
+permissions:
+  issues: write
+
+jobs:
+  auto-assign:
+    name: Assign issue to repo owner
+    runs-on: ubuntu-latest
+    steps:
+      - name: Assign to ${{ github.repository_owner }}
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          ISSUE_URL: ${{ github.event.issue.html_url }}
+          OWNER: ${{ github.repository_owner }}
+        run: gh issue edit "$ISSUE_URL" --add-assignee "$OWNER"