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.

testutil/db.go

@@ -0,0 +1,47 @@
+// Package testutil provides composable test helpers for spinning up
+// real infrastructure (in-memory SQLite, session managers) in
+// integration tests.
+package testutil
+
+import (
+	"database/sql"
+	"io/fs"
+	"testing"
+
+	"github.com/ryanhamamura/c4/db"
+	"github.com/ryanhamamura/c4/db/repository"
+
+	"github.com/pressly/goose/v3"
+	_ "modernc.org/sqlite"
+)
+
+// NewTestDB opens an in-memory SQLite database with the same pragmas as
+// production, runs all goose migrations, and returns the raw connection
+// alongside the sqlc Queries handle. The database is closed automatically
+// when the test finishes.
+func NewTestDB(t *testing.T) (*sql.DB, *repository.Queries) {
+	t.Helper()
+
+	pragmas := "?_pragma=busy_timeout(10000)&_pragma=journal_mode(WAL)&_pragma=journal_size_limit(200000000)&_pragma=synchronous(NORMAL)&_pragma=foreign_keys(ON)&_pragma=temp_store(MEMORY)&_pragma=cache_size(-32000)"
+	database, err := goose.OpenDBWithDriver("sqlite", ":memory:"+pragmas)
+	if err != nil {
+		t.Fatalf("open test database: %v", err)
+	}
+	t.Cleanup(func() { database.Close() }) //nolint:errcheck // test cleanup
+
+	if err := database.Ping(); err != nil {
+		t.Fatalf("ping test database: %v", err)
+	}
+
+	sub, err := fs.Sub(db.MigrationFS, "migrations")
+	if err != nil {
+		t.Fatalf("migrations sub fs: %v", err)
+	}
+	goose.SetBaseFS(sub)
+
+	if err := goose.Up(database, "."); err != nil {
+		t.Fatalf("run migrations: %v", err)
+	}
+
+	return database, repository.New(database)
+}