docs+release: Phase 4 launch artifacts

README hero with real screenshots, install/config/widget docs, goreleaser
for dash + dash-agent, GHCR release workflow, changelog, community files,
agent systemd unit and Dockerfile, version stamping via -X main.version.

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Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

.github/ISSUE_TEMPLATE/feature_request.yml

@@ -0,0 +1,16 @@
+name: Feature request
+description: Suggest an addition
+labels: [enhancement]
+body:
+  - type: textarea
+    id: problem
+    attributes:
+      label: What problem does this solve
+      description: Concrete use case, not just "add X".
+    validations:
+      required: true
+  - type: textarea
+    id: idea
+    attributes:
+      label: Proposed shape
+      description: Optional. How it might look or work.