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.

logging/log.go

@@ -0,0 +1,41 @@
+// Package logging configures zerolog and provides HTTP request logging middleware.
+package logging
+
+import (
+	"io"
+	stdlog "log"
+	"os"
+
+	"github.com/ryanhamamura/c4/config"
+
+	"github.com/rs/zerolog"
+	"github.com/rs/zerolog/log"
+	"github.com/rs/zerolog/pkgerrors"
+)
+
+func SetupLogger(env config.Environment, level zerolog.Level) *zerolog.Logger {
+	zerolog.ErrorStackFieldName = "stack_trace"
+	zerolog.ErrorStackMarshaler = pkgerrors.MarshalStack
+
+	zerolog.SetGlobalLevel(level)
+	zerolog.TimeFieldFormat = zerolog.TimeFormatUnix
+
+	var output io.Writer
+	switch env {
+	case config.Dev:
+		output = zerolog.ConsoleWriter{
+			Out:        os.Stderr,
+			TimeFormat: "2006/01/02 15:04:05",
+		}
+	case config.Prod:
+		output = os.Stderr
+	}
+
+	logger := zerolog.New(output).With().Timestamp().Stack().Logger()
+	zerolog.DefaultContextLogger = &logger
+	log.Logger = logger
+
+	stdlog.SetFlags(0)
+	stdlog.SetOutput(logger)
+	return &logger
+}