docs: AGPLv3 license + public README [#762]

Pre-publication packaging. Full-history secret/badge scans clean;
badge IDs live only in the private access-roster repo.

Detail: https://projects.knownelement.com/issues/762

README.md

@@ -0,0 +1,52 @@
+# pfv-bms — Home Assistant configuration (Turnsys PFV)
+
+Production Home Assistant configuration for a private residence +
+server room: physical-plant environmental monitoring (temperatures,
+power, UPS), server-room badge access control, and alerting.
+
+Licensed under the [GNU AGPLv3](LICENSE) — see [AGPL compliance
+notes](#license) below.
+
+## What lives here
+
+- `configuration.yaml` + `packages/` — the full running config,
+  deployed to the HAOS box via a git-webhook pipeline
+- `packages/doorman.yaml` — badge-scan ingest + whitelist decisions
+  (server-room door access)
+- `packages/plant_snmp.yaml` — fleet temperature/power sensors over
+  SNMP (lm-sensors extends, iDRAC, UPS, PDU relay)
+- `automations.yaml` — tiered thermal alerts + sensor watchdogs
+- `dashboards/` — Lovelace dashboards
+
+## Security model (read this before forking)
+
+- **No secrets in git, ever.** Everything sensitive is `!secret`
+  indirection into an on-box `secrets.yaml` (gitignored). Verified by
+  full-history scans.
+- **Badge IDs are NOT in this repo.** The badge roster lives in a
+  separate *private* repository (`access-roster`, two-human PR gate)
+  and is fetched live at runtime via the gitea API with a secret auth
+  header. This repo contains only the decision logic.
+- Battery-powered room sensors and lock integrations are cloud-fed;
+  their credentials also live in `secrets.yaml`.
+
+## Related
+
+- Work tracking: [Redmine project 55](https://projects.knownelement.com)
+  ([#344](https://projects.knownelement.com/issues/344) HA integration,
+  [#345](https://projects.knownelement.com/issues/345) badge access,
+  [#762](https://projects.knownelement.com/issues/762) publication)
+- Documentation:
+  [VP TechOps on Discourse](https://community.turnsys.com/c/vp-techops)
+- Badge listener/relay code: [KNEL/doorman](https://git.knownelement.com/KNEL/doorman)
+- Wider fleet (Proxmox, DNS, monitoring): [KNEL/PFVCluster](https://git.knownelement.com/KNEL/PFVCluster)
+
+## License
+
+Copyright © 2026 Known Element Enterprises / Charles Wyble.
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU Affero General Public License as
+published by the Free Software Foundation, either version 3 of the
+License, or (at your option) any later version. See [LICENSE](LICENSE)
+for the full text.