M0: repo scaffold, backend skeleton, schema + migrations, dev compose, docs

- Apache-2.0, README, CONTRIBUTING, CODE_OF_CONDUCT, SECURITY, issue templates
- FastAPI app with /api/v1 healthz/readyz/system-status (honest AI disclosure)
- Full SQLAlchemy schema (users, devices, refresh tokens, recordings, assets,
  upload sessions, transcripts, summaries, tags, jobs, exports) + Alembic
  migrations incl. Postgres FTS tsvector columns
- Settings via SHONAR_* env only; local + S3 storage abstraction with
  path-traversal-safe keys
- Docker dev compose (postgres+redis, 127.0.0.1-only); CI workflow; scripts
- shared/openapi.json contract generated from app

CODE_OF_CONDUCT.md

@@ -0,0 +1,29 @@
+# Contributor Code of Conduct
+
+Version 2.1 (Contributor Covenant)
+
+## Our Pledge
+
+We as members, contributors, and leaders pledge to make participation in our
+community 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, caste, religion, or sexual identity
+and orientation.
+
+We pledge to act and interact in ways that contribute to an open, welcoming,
+diverse, inclusive, and healthy community.
+
+## Enforcement
+
+Instances of abusive, harassing, or otherwise unacceptable behavior may be
+reported to the project maintainers at the contact address listed in this
+repository's security policy. All complaints will be reviewed and investigated
+promptly and fairly.
+
+Project maintainers who do not follow or enforce the Code of Conduct in good
+faith may face temporary or permanent repercussions as determined by other
+members of the project's leadership.
+
+This Code of Conduct is adapted from the Contributor Covenant, version 2.1,
+available at https://www.contributor-covenant.org/version/2/1/code_of_conduct/