docs: REUSE.md introduced — reuse map (hub+website+scripts+manifests) + reuse_refs_check.py gate + consolidated cross-repo REPORT

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PSK5g6qYLknKj8u3QAFEr6

CLAUDE.md

@@ -11,6 +11,7 @@ This repo (`felhom.eu`) contains:
 - **Architecture docs** (`documentation/`) — the **authoritative design home for the whole Felhom system**: `architecture/01..05-*.md` (topology/trust, controller module map, host-agent, signing, hub), `proxmox-platform.md`, and `tests/phase{0,1-2,3,4}-findings.md`. Read these before designing.
 
 See `README.md` for full architecture/DNS/email/SEO docs. See `TASK.md` for the current task (if any).
+See `REUSE.md` before writing new code.
 
 ## The Felhom system (so the hub's role is in context)
 
@@ -54,6 +55,8 @@ The planning/architecture assistant ("project Claude", in claude.ai) writes spec
 >
 > **Never write secrets** — tokens, passwords, private keys, API keys — into `CHANGELOG.md`, `REPORT.md`, or any committed file. Reference them as "stored out-of-band" instead.
 
+- Update `REUSE.md` if you added/changed/deprecated a shared helper or pattern (same commit).
+
 ## Tech stack (Hub)
 
 - **Language:** Go 1.24+ (build server is go1.26.0).