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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CODE_OF_CONDUCT.md

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+# Code of Conduct
+
+This project follows the [Contributor Covenant](https://www.contributor-covenant.org/),
+version 2.1.
+
+## Our pledge
+
+We pledge to make participation in this project a harassment-free experience
+for everyone, regardless of age, body size, visible or invisible disability,
+ethnicity, sex characteristics, gender identity and expression, level of
+experience, education, socio-economic status, nationality, personal appearance,
+race, religion, or sexual identity and orientation.
+
+## Our standards
+
+Examples of behavior that contributes to a positive environment:
+
+- Demonstrating empathy and kindness toward other people
+- Being respectful of differing opinions, viewpoints, and experiences
+- Giving and gracefully accepting constructive feedback
+- Accepting responsibility and apologizing to those affected by our mistakes
+- Focusing on what is best for the community
+
+Examples of unacceptable behavior:
+
+- The use of sexualized language or imagery, and sexual attention or advances
+- Trolling, insulting or derogatory comments, and personal or political attacks
+- Public or private harassment
+- Publishing others' private information without explicit permission
+- Other conduct which could reasonably be considered inappropriate in a
+  professional setting
+
+## Enforcement
+
+Instances of unacceptable behavior may be reported to the maintainer via
+GitHub (@Dvorinka). All complaints will be reviewed and investigated promptly
+and fairly. The full enforcement guidelines are at
+https://www.contributor-covenant.org/version/2/1/code_of_conduct.html