fix(brand-questions): accept generic search terms in lexicon validation

Search terms like "全屋定制" or "GEO排名优化" were rejected as invalid because
both the Vue candidate validator and the Go question_metadata classifier
required interrogative cues (什么/如何/为什么/...). Lexicon entries are search
terms, not questions, so require only letters or digits plus the existing
4-char minimum. Rename helpers to searchTermLooksValid/questionLooksValid
to reflect the looser semantics, and relabel the navigation entry from
"公司和词库" to "品牌和词库" to match the actual domain.

server/internal/tenant/app/question_metadata_classify.go

@@ -123,17 +123,14 @@ func questionLooksValid(text string) bool {
 	if utf8.RuneCountInString(trimmed) < 4 {
 		return false
 	}
-	hasLetterOrNumber := false
+	hasSearchTermChar := false
 	for _, r := range trimmed {
 		if unicode.IsLetter(r) || unicode.IsNumber(r) {
-			hasLetterOrNumber = true
+			hasSearchTermChar = true
 			break
 		}
 	}
-	if !hasLetterOrNumber {
-		return false
-	}
-	return containsAny(strings.ToLower(trimmed), []string{"?", "？", "什么", "如何", "怎么", "哪", "为什么", "是否", "能不能", "适合", "区别", "对比", "推荐"})
+	return hasSearchTermChar
 }
 
 func containsAny(value string, needles []string) bool {

server/internal/tenant/app/question_search_term_validation_test.go

@@ -0,0 +1,48 @@
+package app
+
+import "testing"
+
+func TestQuestionLooksValidAcceptsGenericSearchTerms(t *testing.T) {
+	tests := []string{
+		"全屋定制",
+		"GEO排名优化",
+		"AI搜索排名",
+	}
+
+	for _, text := range tests {
+		if !questionLooksValid(text) {
+			t.Fatalf("questionLooksValid(%q) = false, want true", text)
+		}
+	}
+}
+
+func TestBuildCandidateKeepsGenericSearchTermSavable(t *testing.T) {
+	candidate := buildCandidate(
+		"全屋定制",
+		QuestionSourceManual,
+		false,
+		map[string]struct{}{},
+		&questionBrandContext{BrandName: "安徽海翔家居用品销售有限公司"},
+	)
+
+	if candidate.TooShort {
+		t.Fatal("expected generic search term not to be marked too short")
+	}
+	if candidate.SuggestSkip {
+		t.Fatal("expected generic search term not to be suggested for skip")
+	}
+}
+
+func TestQuestionLooksValidRejectsEmptyOrTooShortTerms(t *testing.T) {
+	tests := []string{
+		"",
+		"！？。",
+		"AI",
+	}
+
+	for _, text := range tests {
+		if questionLooksValid(text) {
+			t.Fatalf("questionLooksValid(%q) = true, want false", text)
+		}
+	}
+}