fix(tui): move blocking DB IO out of Update/View into tea.Cmds

The TUI ran database queries on the UI goroutine: handleTick called
refreshData every second, which issued four blocking SQLite queries
(GetAllAlerts/GetAllUsers/GetAllNodes/GetAllMaintenanceWindows) and
swallowed their errors; viewDetailPanel ran GetStateChanges — a DB query
— inside View(), on every render (tick, keypress, mouse). A slow disk
stalled input and animation.

Split refreshData into refreshLive() (in-memory engine copies only —
sites + logs — safe every tick) and loadTabDataCmd(), a tea.Cmd that
loads the four DB-backed tables off the UI goroutine and returns a
tabDataMsg. handleTick now refreshes live state every tick but dispatches
the tab-data load only when older than tabRefreshTTL (5s), so tab-bar
counts stay fresh without a per-second query storm. Errors surface to the
log instead of being dropped, and a transient failure keeps the previous
data rather than blanking the view.

The detail panel's state-change history is loaded once on enter via
loadDetailCmd and cached on the model; viewDetailPanel reads the cache,
so View no longer touches the database. Init kicks an initial load so the
dashboard isn't empty on the first frame, and the bare time.Time tick
message is now a named tickMsg (no cross-message collision). The
test-alert handler's raw goroutine becomes a tea.Cmd.

Adds the package's first Update()-driven tests: tab-data load + apply,
error-keeps-previous-data, detail cache with a store-hit counter proving
View does zero IO across repeated renders, and the handleTick throttle.
Full suite green under -race; golangci-lint clean.

internal/tui/data.go

@@ -7,6 +7,7 @@ import (
 
 	"gitea.lerkolabs.com/lerkolabs/uptop/internal/models"
 	"gitea.lerkolabs.com/lerkolabs/uptop/internal/store"
+	tea "github.com/charmbracelet/bubbletea"
 )
 
 func loadCollapsed(s store.Store) map[int]bool {
@@ -80,41 +81,24 @@ func filterSites(sites []models.Site, needle string) []models.Site {
 	return filtered
 }
 
-func (m *Model) refreshData() {
+// refreshLive updates everything sourced from in-memory engine copies — the
+// live site list (sorted + filtered) and the log viewport. It does no database
+// IO, so it is safe to call on every tick. DB-backed tab data is loaded
+// separately via loadTabDataCmd.
+func (m *Model) refreshLive() {
 	allSites := m.engine.GetAllSites()
 	ordered := sortSitesForDisplay(allSites, m.collapsed)
 	if m.filterText != "" {
 		ordered = filterSites(ordered, m.filterText)
 	}
 	m.sites = ordered
-
-	if alerts, err := m.store.GetAllAlerts(); err == nil {
-		m.alerts = alerts
-	}
-	if m.isAdmin {
-		if users, err := m.store.GetAllUsers(); err == nil {
-			m.users = users
-		}
-	}
-	if nodes, err := m.store.GetAllNodes(); err == nil {
-		m.nodes = nodes
-	}
-	if windows, err := m.store.GetAllMaintenanceWindows(100); err == nil {
-		m.maintenanceWindows = windows
-	}
 	m.logViewport.SetContent(strings.Join(m.engine.GetLogs(), "\n"))
+	m.clampCursor()
+}
 
-	listLen := len(m.sites)
-	switch m.currentTab {
-	case 1:
-		listLen = len(m.alerts)
-	case 3:
-		listLen = len(m.nodes)
-	case 4:
-		listLen = len(m.maintenanceWindows)
-	case 5:
-		listLen = len(m.users)
-	}
+// clampCursor keeps the cursor and scroll offset within the current tab's list.
+func (m *Model) clampCursor() {
+	listLen := m.currentListLen()
 	if listLen > 0 && m.cursor >= listLen {
 		m.cursor = listLen - 1
 	}
@@ -122,3 +106,42 @@ func (m *Model) refreshData() {
 		m.tableOffset = m.cursor
 	}
 }
+
+// loadTabDataCmd returns a tea.Cmd that loads the DB-backed tab tables off the
+// UI goroutine. The closure reads only stable fields (store, isAdmin) and never
+// mutates the model; results come back as a tabDataMsg. On the first store
+// error it returns an error-only msg so the model keeps its previous data.
+func (m *Model) loadTabDataCmd() tea.Cmd {
+	st := m.store
+	isAdmin := m.isAdmin
+	return func() tea.Msg {
+		alerts, err := st.GetAllAlerts()
+		if err != nil {
+			return tabDataMsg{err: err}
+		}
+		var users []models.User
+		if isAdmin {
+			if users, err = st.GetAllUsers(); err != nil {
+				return tabDataMsg{err: err}
+			}
+		}
+		nodes, err := st.GetAllNodes()
+		if err != nil {
+			return tabDataMsg{err: err}
+		}
+		maint, err := st.GetAllMaintenanceWindows(100)
+		if err != nil {
+			return tabDataMsg{err: err}
+		}
+		return tabDataMsg{alerts: alerts, users: users, nodes: nodes, maint: maint}
+	}
+}
+
+// loadDetailCmd loads the state-change history for the detail panel off the UI
+// goroutine. View renders the cached result rather than querying the DB.
+func (m *Model) loadDetailCmd(siteID int) tea.Cmd {
+	eng := m.engine
+	return func() tea.Msg {
+		return detailDataMsg{siteID: siteID, changes: eng.GetStateChanges(siteID, 5)}
+	}
+}