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_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:",
+	}
+}