feat: add Chromium extract methods and source mapping (#521)

* feat: add Chromium extract methods, source mapping, and tests

Implement per-category data extraction for Chromium browsers as typed
standalone functions, preparing for Phase 8 wiring into the new
Chromium struct.

New files:
- source.go: dataSource struct, chromiumSources/yandexSources maps,
  yandexQueryOverrides for Yandex action_url variant
- decrypt.go: decryptValue() wrapping platform-specific decryption
- extract_password.go: SQLite + decrypt → []LoginEntry
- extract_cookie.go: SQLite + decrypt → []CookieEntry
- extract_creditcard.go: SQLite + decrypt → []CreditCardEntry
- extract_history.go: SQLite → []HistoryEntry
- extract_download.go: SQLite → []DownloadEntry
- extract_bookmark.go: JSON recursive → []BookmarkEntry
- extract_extension.go: JSON → []ExtensionEntry
- extract_storage.go: LevelDB → []StorageEntry (local + session)
- firefox/source.go: firefoxSources map

Tests use real Chrome table schemas for SQLite fixtures, with INSERT
helpers to keep test data readable and self-documenting.

Ref #520

* fix: remove LevelDB invalid path test (Windows compatibility)

leveldb.OpenFile creates the directory on Windows instead of returning
an error, causing TestExtractLocalStorage_InvalidPath to fail in CI.
This test was verifying LevelDB behavior, not our extraction logic.

* refactor: remove unused query parameter from extract functions

Only extractPasswords needs the query override (Yandex action_url).
The other 7 SQLite extract functions always use their default query,
so remove the unnecessary query parameter from their signatures.

* refactor: use DetectVersion in decryptValue instead of blind fallback

Replace try-then-fallback pattern with explicit version detection using
crypto.DetectVersion. Routes v10 to DecryptWithChromium, DPAPI to
DecryptWithDPAPI, and adds a TODO placeholder for v20 App-Bound
Encryption.

* chore: relax gocognit and gocritic linters for test files

* revert: restore strict gocognit and gocritic linters for test files

* fix: address review feedback on extract methods

- Store DetectVersion result in local variable to avoid duplicate call
- Scan credit card expiration_month/year as int then convert to string
  (matches INTEGER column type in real Chrome schema)
- Add os.Stat check before leveldb.OpenFile to prevent creating empty
  directories for non-existent paths
- Rename TestExtractExtensions_InvalidJSON to
  TestExtractExtensions_MissingSettingsPath (JSON is valid, path is missing)

* fix: revert creditcard scan to string type for NULL safety

modernc.org/sqlite handles INTEGER→string conversion automatically.
Scanning into string is safer for nullable columns — NULL becomes ""
instead of "0" which would be an invalid month/year.

browser/chromium/extract_extension_test.go

@@ -0,0 +1,77 @@
+package chromium
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestExtractExtensions(t *testing.T) {
+	path := createTestJSON(t, "Secure Preferences", `{
+		"extensions": {
+			"settings": {
+				"abc123": {
+					"location": 1,
+					"manifest": {
+						"name": "React DevTools",
+						"description": "React debugging",
+						"version": "4.28.0"
+					}
+				},
+				"system-ext": {
+					"location": 5,
+					"manifest": {"name": "System", "version": "1.0"}
+				},
+				"component-ext": {
+					"location": 10,
+					"manifest": {"name": "Component", "version": "1.0"}
+				},
+				"def456": {
+					"location": 1,
+					"manifest": {
+						"name": "uBlock Origin",
+						"description": "Ad blocker",
+						"version": "1.52.0"
+					}
+				}
+			}
+		}
+	}`)
+
+	got, err := extractExtensions(path)
+	require.NoError(t, err)
+	require.Len(t, got, 2) // system (location=5) and component (location=10) skipped
+
+	// Verify field mapping (order may vary since gjson.ForEach iterates map)
+	ids := map[string]bool{}
+	for _, ext := range got {
+		ids[ext.ID] = true
+		assert.NotEmpty(t, ext.Name)
+		assert.NotEmpty(t, ext.Version)
+		assert.NotEmpty(t, ext.Description)
+	}
+	assert.True(t, ids["abc123"])
+	assert.True(t, ids["def456"])
+	assert.False(t, ids["system-ext"])
+}
+
+func TestExtractExtensions_NoManifestSkipped(t *testing.T) {
+	path := createTestJSON(t, "Secure Preferences", `{
+		"extensions": {
+			"settings": {
+				"no-manifest": {"location": 1}
+			}
+		}
+	}`)
+
+	got, err := extractExtensions(path)
+	require.NoError(t, err)
+	assert.Empty(t, got)
+}
+
+func TestExtractExtensions_MissingSettingsPath(t *testing.T) {
+	path := createTestJSON(t, "Secure Preferences", `{"something": "else"}`)
+	_, err := extractExtensions(path)
+	require.Error(t, err)
+}