fix: revert .golangci.yml to main, fix all lint issues in code

- Restore original .golangci.yml from main (no linter config changes)
- Reduce complexity in dispatchCommand via command map pattern
- Extract helpers in api.go: respondError, internalError, normalizeChannel,
  handleCreateUserError, handleChangeNickError, partAndCleanup, broadcastTopic
- Split PollMessages into buildPollPath + decodePollResponse
- Add t.Parallel() to all tests, make subtests independent
- Extract test fx providers into named functions to reduce funlen
- Use mutex to serialize viper access in parallel tests
- Extract PRIVMSG constant, add nolint for gosec false positives
- Split long test functions into focused test cases
- Add blank lines before expressions per wsl_v5

internal/db/queries_test.go

@@ -349,10 +349,12 @@ func TestSetTopic(t *testing.T) {
 	}
 }
 
-func TestInsertAndPollMessages(t *testing.T) {
-	t.Parallel()
+func insertTestMessage(
+	t *testing.T,
+	database *db.Database,
+) (int64, int64) {
+	t.Helper()
 
-	database := setupTestDB(t)
 	ctx := t.Context()
 
 	uid, _, err := database.CreateUser(ctx, "poller")
@@ -374,10 +376,19 @@ func TestInsertAndPollMessages(t *testing.T) {
 		t.Fatal(err)
 	}
 
+	return uid, dbID
+}
+
+func TestInsertAndPollMessages(t *testing.T) {
+	t.Parallel()
+
+	database := setupTestDB(t)
+	uid, _ := insertTestMessage(t, database)
+
 	const batchSize = 10
 
 	msgs, lastQID, err := database.PollMessages(
-		ctx, uid, 0, batchSize,
+		t.Context(), uid, 0, batchSize,
 	)
 	if err != nil {
 		t.Fatal(err)
@@ -400,7 +411,7 @@ func TestInsertAndPollMessages(t *testing.T) {
 	}
 
 	msgs, _, _ = database.PollMessages(
-		ctx, uid, lastQID, batchSize,
+		t.Context(), uid, lastQID, batchSize,
 	)
 
 	if len(msgs) != 0 {