feat(legal): imprint & privacy notices, "Über MindSift"

- LEGAL_IMPRINT_/LEGAL_PRIVACY_ URL and Markdown (inline or *_FILE);
  only http(s) URLs accepted
- /auth/status exposes legal info; public GET /legal/{imprint|privacy}
- Links on login/setup screen and in the settings footer: URL opens a new
  tab, Markdown a reading modal; hidden when nothing is configured
- "Über MindSift" modal (version, license, repository) in settings and help
- Docs and compose/env examples

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/api/server.go

@@ -83,6 +83,7 @@ func (s *Server) Router() http.Handler {
 	// Public Health, Setup & Auth Routes
 	r.Get("/api/v1/health", s.handleHealth)
 	r.Get("/api/v1/auth/status", s.handleAuthStatus)
+	r.Get("/api/v1/legal/{type}", s.handleLegalText)
 	r.Post("/api/v1/auth/setup", s.handleFirstBootSetup)
 	r.Post("/api/v1/auth/register", s.handleRegister)
 	r.Post("/api/v1/auth/login", s.handleLogin)
@@ -458,9 +459,32 @@ func (s *Server) handleAuthStatus(w http.ResponseWriter, r *http.Request) {
 		"instanceName":      instanceName,
 		"demoMode":          s.cfg.DemoMode,
 		"sharingMode":       s.store.SharingMode(),
+		// Public so the login screen can link Impressum and Datenschutz
+		"legal": map[string]interface{}{
+			"imprintUrl":        s.cfg.Legal.ImprintURL,
+			"hasImprintContent": s.cfg.Legal.ImprintContent != "",
+			"privacyUrl":        s.cfg.Legal.PrivacyURL,
+			"hasPrivacyContent": s.cfg.Legal.PrivacyContent != "",
+		},
 	})
 }
 
+// handleLegalText serves the configured Markdown of the imprint or privacy notice (public, no login).
+func (s *Server) handleLegalText(w http.ResponseWriter, r *http.Request) {
+	content := ""
+	switch chi.URLParam(r, "type") {
+	case "imprint":
+		content = s.cfg.Legal.ImprintContent
+	case "privacy":
+		content = s.cfg.Legal.PrivacyContent
+	}
+	if content == "" {
+		writeError(w, http.StatusNotFound, "Kein Text hinterlegt")
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]string{"content": content})
+}
+
 func (s *Server) handleFirstBootSetup(w http.ResponseWriter, r *http.Request) {
 	count, err := s.store.CountUsers()
 	if err != nil || count > 0 {