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_prod.go

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