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_scenario_test.go

@@ -0,0 +1,60 @@
+package channelserver
+
+import (
+	"testing"
+
+	"github.com/jmoiron/sqlx"
+)
+
+func setupScenarioRepo(t *testing.T) (*ScenarioRepository, *sqlx.DB) {
+	t.Helper()
+	db := SetupTestDB(t)
+	repo := NewScenarioRepository(db)
+	t.Cleanup(func() { TeardownTestDB(t, db) })
+	return repo, db
+}
+
+func TestRepoScenarioGetCountersEmpty(t *testing.T) {
+	repo, _ := setupScenarioRepo(t)
+
+	counters, err := repo.GetCounters()
+	if err != nil {
+		t.Fatalf("GetCounters failed: %v", err)
+	}
+	if len(counters) != 0 {
+		t.Errorf("Expected 0 counters, got: %d", len(counters))
+	}
+}
+
+func TestRepoScenarioGetCounters(t *testing.T) {
+	repo, db := setupScenarioRepo(t)
+
+	if _, err := db.Exec("INSERT INTO scenario_counter (id, scenario_id, category_id) VALUES (1, 100, 0)"); err != nil {
+		t.Fatalf("Setup failed: %v", err)
+	}
+	if _, err := db.Exec("INSERT INTO scenario_counter (id, scenario_id, category_id) VALUES (2, 200, 1)"); err != nil {
+		t.Fatalf("Setup failed: %v", err)
+	}
+
+	counters, err := repo.GetCounters()
+	if err != nil {
+		t.Fatalf("GetCounters failed: %v", err)
+	}
+	if len(counters) != 2 {
+		t.Fatalf("Expected 2 counters, got: %d", len(counters))
+	}
+
+	// Check both values exist (order may vary)
+	found100, found200 := false, false
+	for _, c := range counters {
+		if c.MainID == 100 {
+			found100 = true
+		}
+		if c.MainID == 200 {
+			found200 = true
+		}
+	}
+	if !found100 || !found200 {
+		t.Errorf("Expected scenario_ids 100 and 200, got: %+v", counters)
+	}
+}