feat: add language support and tests for English and Chinese seed data

- Introduced a new package `seedlang` to handle language parsing and constants for English and Chinese.
- Updated `Init` functions across various modules (kb, quickreply, skill, tag) to accept a language parameter.
- Implemented English seed data for FAQs, quick replies, skills, and tags, ensuring no Chinese text is present in English data.
- Added tests to verify that English seed data does not contain Chinese characters.
- Removed outdated README file from the kb test data directory.
- Created new test files for channel and kb to validate the absence of Chinese text in English seed data.

cmd/testdata/seedlang/language.go

@@ -0,0 +1,25 @@
+package seedlang
+
+import (
+	"fmt"
+	"strings"
+)
+
+type Language string
+
+const (
+	Chinese Language = "zh"
+	English Language = "en"
+)
+
+func Parse(raw string) (Language, error) {
+	normalized := strings.ToLower(strings.TrimSpace(raw))
+	switch normalized {
+	case "", "zh", "zh-cn", "chinese":
+		return Chinese, nil
+	case "en", "en-us", "english":
+		return English, nil
+	default:
+		return "", fmt.Errorf("unsupported testdata language %q, supported: zh, en", raw)
+	}
+}