server <- function(input, output, session) {
  
  # ── Globaler Navigations-Bus ───────────────────────────────────────────────
  r_global <- reactiveValues(
    # Navigation
    active_tab         = NULL,
    nav_history        = list(),   # ← Stack der letzten Positionen
    
    # Filter + Sprungziele
    buchungen_filter   = "alle",
    jump_to_entry_id   = NULL,
    jump_to_account_id = NULL,
    jump_to_contact_id = NULL,
    jump_to_project_id = NULL
  )
  
  # ── Tab-Wechsel ────────────────────────────────────────────────────────────
  observeEvent(r_global$active_tab, ignoreInit = TRUE, {
    req(r_global$active_tab)
    cat("Tab-Wechsel zu:", r_global$active_tab, "\n")
    updateTabItems(session, "tabs", selected = r_global$active_tab)
    r_global$active_tab <- NULL
  })
  
  observeEvent(input$back_btn, {
    req(length(r_global$nav_history) > 0)
    
    # Letzten Zustand holen und Stack kürzen
    last <- tail(r_global$nav_history, 1)[[1]]
    r_global$nav_history <- head(r_global$nav_history, -1)
    
    # Zurückspringen
    updateTabItems(session, "tabs", selected = last$tab)
    
    # Zustand wiederherstellen — je nach Tab
    if (last$tab == "konten") {
      r_global$jump_to_account_name <- last$account_name
    }
  })
  
  # ── Filter-Buttons (falls in der Navbar oder UI definiert) ─────────────────
  observeEvent(input$filter_alle,  { r_global$buchungen_filter <- "alle"  })
  observeEvent(input$filter_giro,  { r_global$buchungen_filter <- "giro"  })
  observeEvent(input$filter_monat, { r_global$buchungen_filter <- "monat" })
  
  # ── Module ─────────────────────────────────────────────────────────────────
  accountsServer("accounts_tab",     conn, r_global)
  buchungenServer("buchungen_tab", conn, r_global)
}