feat: App-Version 0.9.1 + Modulversionsnummern

- version.go: AppVersion + Modules-Map (pro Modul interne Versionsnummer)
- GET /api/version: liefert App- und Modulversionen (ohne Auth)
- archivmail version: zeigt App- und Modulversionen in CLI
- version-Konstante aus cmd_import.go entfernt (war falsche Stelle)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/api/server.go

@@ -73,11 +73,13 @@ type Server struct {
 	pop3Store     *pop3store.Store
 	pop3Importer  *pop3store.Importer
 	uploadJobs    sync.Map // jobID → *UploadJob
-	labels        *labelstore.Store         // PROJ-9: label management
+	labels        *labelstore.Store
 	ldapStore         *ldapcfg.Store
 	tenantStore       *tenantstore.Store
-	tenantLdapStore   *ldapcfg.TenantStore   // PROJ-23: per-tenant LDAP config
-	idxMgr            *index.TenantIndexManager // PROJ-21 Phase 4: per-tenant Xapian index
+	tenantLdapStore   *ldapcfg.TenantStore
+	idxMgr            *index.TenantIndexManager
+	appVersion    string
+	moduleVersions map[string]string
 }
 
 // SetSMTPDaemon wires the SMTP daemon into the API server after construction.
@@ -103,6 +105,12 @@ func (s *Server) SetIndexManager(mgr *index.TenantIndexManager) {
 	s.idxMgr = mgr
 }
 
+// SetVersion wires app version and module versions into the API server.
+func (s *Server) SetVersion(appVersion string, modules map[string]string) {
+	s.appVersion = appVersion
+	s.moduleVersions = modules
+}
+
 // New creates and wires up a new API server.
 func New(
 	cfg config.APIConfig,
@@ -139,6 +147,7 @@ func (s *Server) authAdmin(h http.HandlerFunc) http.HandlerFunc {
 
 func (s *Server) routes() {
 	s.mux.HandleFunc("GET /api/health", s.handleHealth)
+	s.mux.HandleFunc("GET /api/version", s.handleVersion)
 	s.mux.HandleFunc("POST /api/auth/login", s.handleLogin)
 	s.mux.HandleFunc("GET /api/auth/me", s.auth(s.handleMe))
 	s.mux.HandleFunc("POST /api/auth/logout", s.auth(s.handleLogout))

internal/api/version_handlers.go

@@ -0,0 +1,12 @@
+package api
+
+import "net/http"
+
+// handleVersion liefert App- und Modulversionen.
+// GET /api/version — öffentlich (kein Auth erforderlich).
+func (s *Server) handleVersion(w http.ResponseWriter, r *http.Request) {
+	writeJSON(w, http.StatusOK, map[string]interface{}{
+		"version": s.appVersion,
+		"modules": s.moduleVersions,
+	})
+}