refactor: decompose monitor.go and sqlstore.go into focused files

Split monitor.go (1131→350 lines) into alerts.go, checks.go,
sites.go, and maintenance.go by concern. Split sqlstore.go
(833→470 lines) into sqlstore_alerts.go, sqlstore_history.go,
and sqlstore_maintenance.go by domain. Tests move with their
implementation. Pure reorganization — no behavioral changes.

internal/monitor/sites_test.go

@@ -0,0 +1,133 @@
+package monitor
+
+import (
+	"testing"
+	"time"
+
+	"gitea.lerkolabs.com/lerkolabs/uptop/internal/models"
+)
+
+func TestUpdateSiteConfig_PreservesRuntime(t *testing.T) {
+	ms := newMockStore()
+	e := newTestEngine(ms)
+	site := models.Site{
+		SiteConfig: models.SiteConfig{ID: 1, Name: "test", URL: "http://old.com"},
+		SiteState:  models.SiteState{Status: "DOWN", FailureCount: 3, Latency: 100 * time.Millisecond},
+	}
+	injectSite(e, site)
+
+	updated := models.SiteConfig{ID: 1, Name: "test", URL: "http://new.com", Interval: 60}
+	e.UpdateSiteConfig(updated)
+
+	s, _ := getSite(e, 1)
+	if s.URL != "http://new.com" {
+		t.Errorf("expected URL updated, got %s", s.URL)
+	}
+	if s.Status != "DOWN" {
+		t.Errorf("expected Status preserved, got %s", s.Status)
+	}
+	if s.FailureCount != 3 {
+		t.Errorf("expected FailureCount preserved, got %d", s.FailureCount)
+	}
+	if s.Latency != 100*time.Millisecond {
+		t.Errorf("expected Latency preserved, got %v", s.Latency)
+	}
+}
+
+func TestRemoveSite_CleansUp(t *testing.T) {
+	ms := newMockStore()
+	e := newTestEngine(ms)
+	site := models.Site{
+		SiteConfig: models.SiteConfig{ID: 1, Name: "test", Type: "push", Token: "tok1"},
+		SiteState:  models.SiteState{Status: "UP"},
+	}
+	injectSite(e, site)
+	e.recordCheck(1, 5*time.Millisecond, true)
+
+	e.RemoveSite(1)
+
+	if _, ok := getSite(e, 1); ok {
+		t.Error("expected site removed from liveState")
+	}
+	if e.RecordHeartbeat("tok1") {
+		t.Error("expected token removed from index")
+	}
+	if _, ok := e.GetHistory(1); ok {
+		t.Error("expected history removed")
+	}
+}
+
+func TestToggleSitePause(t *testing.T) {
+	ms := newMockStore()
+	e := newTestEngine(ms)
+	site := models.Site{
+		SiteConfig: models.SiteConfig{ID: 1, Name: "test"},
+		SiteState:  models.SiteState{Status: "UP"},
+	}
+	injectSite(e, site)
+
+	paused := e.ToggleSitePause(1)
+	if !paused {
+		t.Error("expected paused=true after first toggle")
+	}
+	s, _ := getSite(e, 1)
+	if !s.Paused {
+		t.Error("expected Paused=true in state")
+	}
+
+	paused = e.ToggleSitePause(1)
+	if paused {
+		t.Error("expected paused=false after second toggle")
+	}
+}
+
+func TestToggleSitePause_NonexistentSite(t *testing.T) {
+	ms := newMockStore()
+	e := newTestEngine(ms)
+	if e.ToggleSitePause(999) {
+		t.Error("expected false for nonexistent site")
+	}
+}
+
+func TestGetAllSites_ReturnsCopy(t *testing.T) {
+	ms := newMockStore()
+	e := newTestEngine(ms)
+	injectSite(e, models.Site{
+		SiteConfig: models.SiteConfig{ID: 1, Name: "s1"},
+		SiteState:  models.SiteState{Status: "UP"},
+	})
+	injectSite(e, models.Site{
+		SiteConfig: models.SiteConfig{ID: 2, Name: "s2"},
+		SiteState:  models.SiteState{Status: "DOWN"},
+	})
+
+	sites := e.GetAllSites()
+	if len(sites) != 2 {
+		t.Fatalf("expected 2 sites, got %d", len(sites))
+	}
+	sites[0].Name = "mutated"
+
+	fresh := e.GetAllSites()
+	for _, s := range fresh {
+		if s.Name == "mutated" {
+			t.Error("GetAllSites returned reference, not copy")
+		}
+	}
+}
+
+func TestGetLiveState_ReturnsCopy(t *testing.T) {
+	ms := newMockStore()
+	e := newTestEngine(ms)
+	injectSite(e, models.Site{
+		SiteConfig: models.SiteConfig{ID: 1, Name: "s1"},
+		SiteState:  models.SiteState{Status: "UP"},
+	})
+
+	state := e.GetLiveState()
+	state[1] = models.Site{SiteConfig: models.SiteConfig{Name: "mutated"}}
+
+	fresh := e.GetLiveState()
+	if fresh[1].Name == "mutated" {
+		t.Error("GetLiveState returned reference, not copy")
+	}
+}