feat: add browserdata/datautil helpers (#513)

* feat: add browserdata/datautil helpers (QuerySQLite, QueryRows, DecryptChromiumValue)

Phase 2 of architecture refactoring (RFC-002 Section 3):

- datautil/sqlite.go: QuerySQLite() — shared SQLite open/query/scan helper
  with optional journal_mode=off for Firefox databases
- datautil/query.go: QueryRows[T]() — generic helper (Go 1.20) that wraps
  QuerySQLite and collects results into a typed slice
- datautil/decrypt.go: DecryptChromiumValue() — unified Chromium decryption
  (DPAPI first, then AES-GCM/CBC fallback)
- datautil/sqlite_test.go: tests for all helpers

* refactor: move DecryptChromiumValue from datautil to browser/chromium

- Remove browserdata/datautil/decrypt.go (Chromium-specific, not a generic util)
- Will be added as browser/chromium/decrypt.go (unexported decryptValue)
  in the chromium extract methods PR
- Update RFCs to reflect the change
- Remove decrypt test from datautil tests

* refactor: move datautil to utils/sqliteutil for consistency

- Rename browserdata/datautil/ → utils/sqliteutil/
- Aligns with existing utils/ convention (fileutil, typeutil, byteutil)
- QuerySQLite/QueryRows are generic SQLite helpers, not browserdata-specific
- Update package name from datautil to sqliteutil
- Update both RFCs to reflect new location

* fix: apply review suggestions for sqliteutil

- QuerySQLite: validate dbPath exists before sql.Open to prevent
  silently creating empty databases
- Tests: check db.Close() errors with require.NoError

utils/sqliteutil/sqlite_test.go

@@ -0,0 +1,138 @@
+package sqliteutil
+
+import (
+	"database/sql"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestQuerySQLite(t *testing.T) {
+	// Create a temp SQLite database
+	dir := t.TempDir()
+	dbPath := filepath.Join(dir, "test.db")
+
+	db, err := sql.Open("sqlite", dbPath)
+	require.NoError(t, err)
+
+	_, err = db.Exec("CREATE TABLE items (id INTEGER, name TEXT)")
+	require.NoError(t, err)
+	_, err = db.Exec("INSERT INTO items VALUES (1, 'alpha'), (2, 'beta'), (3, 'gamma')")
+	require.NoError(t, err)
+	require.NoError(t, db.Close())
+
+	// Query using our helper
+	var names []string
+	err = QuerySQLite(dbPath, false, "SELECT name FROM items ORDER BY id", func(rows *sql.Rows) error {
+		var name string
+		if err := rows.Scan(&name); err != nil {
+			return err
+		}
+		names = append(names, name)
+		return nil
+	})
+
+	assert.NoError(t, err)
+	assert.Equal(t, []string{"alpha", "beta", "gamma"}, names)
+}
+
+func TestQuerySQLite_JournalOff(t *testing.T) {
+	dir := t.TempDir()
+	dbPath := filepath.Join(dir, "test.db")
+
+	db, err := sql.Open("sqlite", dbPath)
+	require.NoError(t, err)
+	_, err = db.Exec("CREATE TABLE t (v TEXT)")
+	require.NoError(t, err)
+	_, err = db.Exec("INSERT INTO t VALUES ('ok')")
+	require.NoError(t, err)
+	require.NoError(t, db.Close())
+
+	var values []string
+	err = QuerySQLite(dbPath, true, "SELECT v FROM t", func(rows *sql.Rows) error {
+		var v string
+		if err := rows.Scan(&v); err != nil {
+			return err
+		}
+		values = append(values, v)
+		return nil
+	})
+	assert.NoError(t, err)
+	assert.Equal(t, []string{"ok"}, values)
+}
+
+func TestQuerySQLite_FileNotFound(t *testing.T) {
+	err := QuerySQLite("/nonexistent/path.db", false, "SELECT 1", func(rows *sql.Rows) error {
+		return nil
+	})
+	assert.Error(t, err)
+}
+
+func TestQuerySQLite_BadQuery(t *testing.T) {
+	dir := t.TempDir()
+	dbPath := filepath.Join(dir, "test.db")
+
+	db, err := sql.Open("sqlite", dbPath)
+	require.NoError(t, err)
+	_, err = db.Exec("CREATE TABLE t (v TEXT)")
+	require.NoError(t, err)
+	require.NoError(t, db.Close())
+
+	err = QuerySQLite(dbPath, false, "SELECT nonexistent FROM t", func(rows *sql.Rows) error {
+		return nil
+	})
+	assert.Error(t, err)
+}
+
+func TestQueryRows(t *testing.T) {
+	dir := t.TempDir()
+	dbPath := filepath.Join(dir, "test.db")
+
+	db, err := sql.Open("sqlite", dbPath)
+	require.NoError(t, err)
+	_, err = db.Exec("CREATE TABLE users (name TEXT, age INTEGER)")
+	require.NoError(t, err)
+	_, err = db.Exec("INSERT INTO users VALUES ('alice', 30), ('bob', 25)")
+	require.NoError(t, err)
+	require.NoError(t, db.Close())
+
+	type user struct {
+		Name string
+		Age  int
+	}
+
+	users, err := QueryRows(dbPath, false, "SELECT name, age FROM users ORDER BY name",
+		func(rows *sql.Rows) (user, error) {
+			var u user
+			err := rows.Scan(&u.Name, &u.Age)
+			return u, err
+		})
+
+	assert.NoError(t, err)
+	assert.Equal(t, []user{{"alice", 30}, {"bob", 25}}, users)
+}
+
+func TestQueryRows_Empty(t *testing.T) {
+	dir := t.TempDir()
+	dbPath := filepath.Join(dir, "test.db")
+
+	db, err := sql.Open("sqlite", dbPath)
+	require.NoError(t, err)
+	_, err = db.Exec("CREATE TABLE empty (v TEXT)")
+	require.NoError(t, err)
+	require.NoError(t, db.Close())
+
+	results, err := QueryRows(dbPath, false, "SELECT v FROM empty",
+		func(rows *sql.Rows) (string, error) {
+			var v string
+			if err := rows.Scan(&v); err != nil {
+				return "", err
+			}
+			return v, nil
+		})
+
+	assert.NoError(t, err)
+	assert.Nil(t, results)
+}