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- Removed outdated README file from the kb test data directory.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_test.go

@@ -0,0 +1,31 @@
+package seedlang
+
+import "testing"
+
+func TestParseDefaultsToChinese(t *testing.T) {
+	lang, err := Parse("")
+	if err != nil {
+		t.Fatalf("Parse empty returned error: %v", err)
+	}
+	if lang != Chinese {
+		t.Fatalf("Parse empty = %q, want %q", lang, Chinese)
+	}
+}
+
+func TestParseEnglishAliases(t *testing.T) {
+	for _, raw := range []string{"en", "EN", "english", "English"} {
+		lang, err := Parse(raw)
+		if err != nil {
+			t.Fatalf("Parse(%q) returned error: %v", raw, err)
+		}
+		if lang != English {
+			t.Fatalf("Parse(%q) = %q, want %q", raw, lang, English)
+		}
+	}
+}
+
+func TestParseRejectsUnsupportedLanguage(t *testing.T) {
+	if _, err := Parse("fr"); err == nil {
+		t.Fatal("Parse unsupported language returned nil error")
+	}
+}