refactor: adopt portigo infrastructure patterns

Add config package with build-tag-switched dev/prod environments,
structured logging via zerolog, Taskfile for dev workflow, golangci-lint
config, testutil package, and improved DB setup with proper SQLite
pragmas and cleanup. Rename sqlc output package from gen to repository.

Switch to allowlist .gitignore, Alpine+UPX+scratch Dockerfile, and
CI pipeline with test/lint gates before deploy.

config/config.go

@@ -0,0 +1,73 @@
+// Package config provides build-tag-switched application configuration.
+// The global Config singleton is initialized at import time via init()
+// and can be overridden in tests with LoadForTest().
+package config
+
+import (
+	"os"
+	"sync"
+
+	"github.com/joho/godotenv"
+	"github.com/rs/zerolog"
+)
+
+type Environment string
+
+const (
+	Dev  Environment = "dev"
+	Prod Environment = "prod"
+)
+
+type Config struct {
+	Environment Environment
+	Host        string
+	Port        string
+	LogLevel    zerolog.Level
+	AppURL      string
+	DBPath      string
+}
+
+var (
+	Global *Config
+	once   sync.Once
+)
+
+func init() {
+	once.Do(func() {
+		Global = Load()
+	})
+}
+
+func getEnv(key, fallback string) string {
+	if val, ok := os.LookupEnv(key); ok {
+		return val
+	}
+	return fallback
+}
+
+func loadBase() *Config {
+	godotenv.Load() //nolint:errcheck // .env file is optional
+
+	return &Config{
+		Host: getEnv("HOST", "0.0.0.0"),
+		Port: getEnv("PORT", "7331"),
+		LogLevel: func() zerolog.Level {
+			switch os.Getenv("LOG_LEVEL") {
+			case "TRACE":
+				return zerolog.TraceLevel
+			case "DEBUG":
+				return zerolog.DebugLevel
+			case "INFO":
+				return zerolog.InfoLevel
+			case "WARN":
+				return zerolog.WarnLevel
+			case "ERROR":
+				return zerolog.ErrorLevel
+			default:
+				return zerolog.InfoLevel
+			}
+		}(),
+		AppURL: getEnv("APP_URL", "https://games.adriatica.io"),
+		DBPath: getEnv("DB_PATH", "data/c4.db"),
+	}
+}

config/config_dev.go

@@ -0,0 +1,9 @@
+//go:build dev
+
+package config
+
+func Load() *Config {
+	cfg := loadBase()
+	cfg.Environment = Dev
+	return cfg
+}

config/config_prod.go

@@ -0,0 +1,9 @@
+//go:build !dev
+
+package config
+
+func Load() *Config {
+	cfg := loadBase()
+	cfg.Environment = Prod
+	return cfg
+}

config/config_test_helper.go

@@ -0,0 +1,19 @@
+package config
+
+import (
+	"github.com/rs/zerolog"
+)
+
+// LoadForTest sets config.Global to safe defaults without reading
+// environment variables or .env files. Call this in TestMain or at the
+// top of tests that import packages which depend on config.Global.
+func LoadForTest() {
+	Global = &Config{
+		Environment: Dev,
+		Host:        "127.0.0.1",
+		Port:        "0",
+		LogLevel:    zerolog.WarnLevel,
+		AppURL:      "http://localhost:0",
+		DBPath:      ":memory:",
+	}
+}