§22 S4: release v0.43.0 — invitation surfaces + role-aware empty states (@S4)

Bump VERSION + frontend/package.json to 0.43.0, add the CHANGELOG entry
(minor, non-breaking — additive endpoints + UI, no migration, no change to
existing authz outcomes), and mark Part E slice S4 shipped in the design doc.

Completes @S4 (C2.1–C2.7 invitation + C3.3–C3.5 role-aware empty states).
Next: S5 (in-app create-project + the global directory, C3.1–C3.2).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/package.json

@@ -1,7 +1,7 @@
 {
   "name": "rfc-app-frontend",
   "private": true,
-  "version": "0.42.0",
+  "version": "0.43.0",
   "type": "module",
   "scripts": {
     "dev": "vite",