feat(tui): single-dashboard layout with sidebar and overlay

Replace 3-tab navigation with a single monitoring dashboard.

- Replace tab bar with minimal status line (pulse + counts + version)
- Maintenance becomes a toggleable left sidebar (m key)
  - Compact list: active (●) and scheduled (○) windows
  - Enter opens full-screen detail with end/delete actions
- Settings becomes a centered floating overlay (S key)
  - Alerts/Nodes/Users sub-sections with left/right navigation
  - Full CRUD support inside overlay with returnState tracking
- Remove currentTab, switchTab, tab constants, tab click zones
- Replace deleteTab with deleteKind string for cleaner dispatch
- Separate settingsCursor/settingsOffset from main cursor
- Panel focus: maint → monitors → logs → detail
- Context-sensitive footer key hints per focused panel

internal/tui/view_maint_sidebar.go

@@ -0,0 +1,193 @@
+package tui
+
+import (
+	"fmt"
+	"strings"
+	"time"
+
+	"gitea.lerkolabs.com/lerkolabs/uptop/internal/models"
+	"github.com/charmbracelet/lipgloss"
+)
+
+func (m Model) viewMaintDetailPanel() string {
+	mw := m.findMaintWindow(m.maintDetailID)
+	if mw == nil {
+		return lipgloss.NewStyle().Padding(1, 2).Render(m.st.subtleStyle.Render("Maintenance window not found"))
+	}
+
+	var b strings.Builder
+
+	header := "  " + m.st.subtleStyle.Render("Maintenance >") + " " + m.st.titleStyle.Render(mw.Title)
+	b.WriteString(header + "\n")
+	b.WriteString(m.divider() + "\n")
+
+	row := func(label, value string) {
+		fmt.Fprintf(&b, "  %-16s %s\n", m.st.subtleStyle.Render(label), value)
+	}
+
+	maintType := m.st.maintStyle.Render("maintenance")
+	if mw.Type == "incident" {
+		maintType = m.st.dangerStyle.Render("incident")
+	}
+	row("Type", maintType)
+
+	now := time.Now()
+	if mw.StartTime.After(now) {
+		row("Status", m.st.warnStyle.Render("SCHEDULED"))
+	} else if !mw.EndTime.IsZero() && mw.EndTime.Before(now) {
+		row("Status", m.st.subtleStyle.Render("ENDED"))
+	} else {
+		row("Status", m.st.specialStyle.Render("ACTIVE"))
+	}
+
+	if mw.MonitorID == 0 {
+		row("Monitors", "All")
+	} else {
+		name := fmt.Sprintf("#%d", mw.MonitorID)
+		allSites := m.engine.GetAllSites()
+		for _, s := range allSites {
+			if s.ID == mw.MonitorID {
+				name = s.Name
+				break
+			}
+		}
+		row("Monitors", name)
+	}
+
+	row("Started", mw.StartTime.Format("2006-01-02 15:04"))
+	if mw.EndTime.IsZero() {
+		row("Ends", m.st.subtleStyle.Render("indefinite"))
+	} else {
+		row("Ends", mw.EndTime.Format("2006-01-02 15:04"))
+		if mw.EndTime.After(now) && !mw.StartTime.After(now) {
+			remaining := time.Until(mw.EndTime)
+			row("Remaining", fmtDuration(remaining))
+		}
+		dur := mw.EndTime.Sub(mw.StartTime)
+		row("Duration", fmtDuration(dur))
+	}
+
+	if mw.Description != "" {
+		b.WriteString("\n")
+		row("Description", mw.Description)
+	}
+
+	b.WriteString("\n" + m.divider() + "\n")
+
+	var keys []string
+	isActive := !mw.StartTime.After(now) && (mw.EndTime.IsZero() || mw.EndTime.After(now))
+	if isActive {
+		keys = append(keys, "[x] End")
+	}
+	keys = append(keys, "[d] Delete", "[q/Esc] Back")
+	b.WriteString("  " + m.st.subtleStyle.Render(strings.Join(keys, "  ")))
+
+	return lipgloss.NewStyle().Padding(1, 2).Render(b.String())
+}
+
+func (m Model) activeMaintWindows() []models.MaintenanceWindow {
+	now := time.Now()
+	var out []models.MaintenanceWindow
+	for _, mw := range m.maintenanceWindows {
+		if !mw.EndTime.IsZero() && mw.EndTime.Before(now) {
+			continue
+		}
+		out = append(out, mw)
+	}
+	return out
+}
+
+func (m Model) viewMaintSidebar(width, maxLines int) string {
+	windows := m.activeMaintWindows()
+	if len(windows) == 0 {
+		return m.st.subtleStyle.Render(" No active maintenance")
+	}
+
+	contentW := width - 2
+	if contentW < 10 {
+		contentW = 10
+	}
+
+	start := m.maintOffset
+	if start > len(windows) {
+		start = len(windows)
+	}
+	linesUsed := 0
+	end := start
+	for end < len(windows) && linesUsed+2 <= maxLines {
+		linesUsed += 2
+		end++
+	}
+
+	var lines []string
+	now := time.Now()
+	for i := start; i < end; i++ {
+		mw := windows[i]
+		selected := m.focusedPanel == panelMaint && i == m.maintCursor
+
+		isActive := !mw.StartTime.After(now) && (mw.EndTime.IsZero() || mw.EndTime.After(now))
+
+		var icon string
+		if isActive {
+			icon = m.st.specialStyle.Render("●")
+		} else {
+			icon = m.st.warnStyle.Render("○")
+		}
+
+		title := limitStr(mw.Title, contentW-3)
+		titleLine := " " + icon + " " + title
+
+		var detail string
+		if isActive {
+			if mw.EndTime.IsZero() {
+				detail = m.st.subtleStyle.Render("active · indefinite")
+			} else {
+				remaining := time.Until(mw.EndTime)
+				detail = m.st.subtleStyle.Render("active · " + fmtDuration(remaining))
+			}
+		} else {
+			detail = m.st.subtleStyle.Render(mw.StartTime.Format("Jan 02") + " · " + fmtDuration(mw.EndTime.Sub(mw.StartTime)))
+		}
+		detailLine := "   " + limitStr(detail, contentW-3)
+
+		if selected {
+			sel := m.st.tableSelectedStyle
+			titleLine = sel.Render(lipgloss.NewStyle().Width(contentW).Render(titleLine))
+			detailLine = sel.Render(lipgloss.NewStyle().Width(contentW).Render(detailLine))
+		}
+
+		lines = append(lines, titleLine, detailLine)
+	}
+
+	if len(windows) > end-start {
+		more := fmt.Sprintf(" %d more", len(windows)-(end-start))
+		lines = append(lines, m.st.subtleStyle.Render(more))
+	}
+
+	return strings.Join(lines, "\n")
+}
+
+func (m *Model) scrollMaintCursor(delta int) {
+	windows := m.activeMaintWindows()
+	total := len(windows)
+	if total == 0 {
+		return
+	}
+	m.maintCursor += delta
+	if m.maintCursor < 0 {
+		m.maintCursor = 0
+	}
+	if m.maintCursor >= total {
+		m.maintCursor = total - 1
+	}
+	if m.maintCursor < m.maintOffset {
+		m.maintOffset = m.maintCursor
+	}
+	visible := m.maxTableRows / 2
+	if visible < 1 {
+		visible = 1
+	}
+	if m.maintCursor >= m.maintOffset+visible {
+		m.maintOffset = m.maintCursor - visible + 1
+	}
+}