test(repos): add SQL integration tests for 17 untested repo files

Add 148 integration tests exercising actual SQL against PostgreSQL for
all previously untested repository files. Includes 6 new fixture helpers
in testhelpers_db.go and CI PostgreSQL service configuration.

Discovered and documented existing RecordPurchase SQL bug (ambiguous
column reference in ON CONFLICT clause).

server/channelserver/repo_diva_test.go

@@ -0,0 +1,113 @@
+package channelserver
+
+import (
+	"testing"
+
+	"github.com/jmoiron/sqlx"
+)
+
+func setupDivaRepo(t *testing.T) (*DivaRepository, *sqlx.DB) {
+	t.Helper()
+	db := SetupTestDB(t)
+	repo := NewDivaRepository(db)
+	t.Cleanup(func() { TeardownTestDB(t, db) })
+	return repo, db
+}
+
+func TestRepoDivaInsertAndGetEvents(t *testing.T) {
+	repo, _ := setupDivaRepo(t)
+
+	if err := repo.InsertEvent(1700000000); err != nil {
+		t.Fatalf("InsertEvent failed: %v", err)
+	}
+
+	events, err := repo.GetEvents()
+	if err != nil {
+		t.Fatalf("GetEvents failed: %v", err)
+	}
+	if len(events) != 1 {
+		t.Fatalf("Expected 1 event, got: %d", len(events))
+	}
+	if events[0].StartTime != 1700000000 {
+		t.Errorf("Expected start_time=1700000000, got: %d", events[0].StartTime)
+	}
+}
+
+func TestRepoDivaGetEventsEmpty(t *testing.T) {
+	repo, _ := setupDivaRepo(t)
+
+	events, err := repo.GetEvents()
+	if err != nil {
+		t.Fatalf("GetEvents failed: %v", err)
+	}
+	if len(events) != 0 {
+		t.Errorf("Expected 0 events, got: %d", len(events))
+	}
+}
+
+func TestRepoDivaDeleteEvents(t *testing.T) {
+	repo, _ := setupDivaRepo(t)
+
+	if err := repo.InsertEvent(1700000000); err != nil {
+		t.Fatalf("InsertEvent failed: %v", err)
+	}
+	if err := repo.InsertEvent(1700100000); err != nil {
+		t.Fatalf("InsertEvent failed: %v", err)
+	}
+
+	if err := repo.DeleteEvents(); err != nil {
+		t.Fatalf("DeleteEvents failed: %v", err)
+	}
+
+	events, err := repo.GetEvents()
+	if err != nil {
+		t.Fatalf("GetEvents failed: %v", err)
+	}
+	if len(events) != 0 {
+		t.Errorf("Expected 0 events after delete, got: %d", len(events))
+	}
+}
+
+func TestRepoDivaMultipleEvents(t *testing.T) {
+	repo, _ := setupDivaRepo(t)
+
+	if err := repo.InsertEvent(1700000000); err != nil {
+		t.Fatalf("InsertEvent 1 failed: %v", err)
+	}
+	if err := repo.InsertEvent(1700100000); err != nil {
+		t.Fatalf("InsertEvent 2 failed: %v", err)
+	}
+
+	events, err := repo.GetEvents()
+	if err != nil {
+		t.Fatalf("GetEvents failed: %v", err)
+	}
+	if len(events) != 2 {
+		t.Errorf("Expected 2 events, got: %d", len(events))
+	}
+}
+
+func TestRepoDivaDeleteOnlyDivaEvents(t *testing.T) {
+	repo, db := setupDivaRepo(t)
+
+	// Insert a diva event
+	if err := repo.InsertEvent(1700000000); err != nil {
+		t.Fatalf("InsertEvent failed: %v", err)
+	}
+	// Insert a festa event (should not be deleted)
+	if _, err := db.Exec("INSERT INTO events (event_type, start_time) VALUES ('festa', now())"); err != nil {
+		t.Fatalf("Setup failed: %v", err)
+	}
+
+	if err := repo.DeleteEvents(); err != nil {
+		t.Fatalf("DeleteEvents failed: %v", err)
+	}
+
+	var count int
+	if err := db.QueryRow("SELECT COUNT(*) FROM events WHERE event_type='festa'").Scan(&count); err != nil {
+		t.Fatalf("Verification query failed: %v", err)
+	}
+	if count != 1 {
+		t.Errorf("Expected festa event to survive, got count=%d", count)
+	}
+}