fix: ShareModal shows blank overlay when factoryId is undefined

When clicking "分享链接" for unlinked plans, factoryId is undefined.
The ShareModal's useEffect returned early without setting hasRelationship,
leaving it as null — none of the three conditional branches rendered,
showing only the backdrop overlay with no content.

Fix: when factoryId is missing, set hasRelationship=false directly to
show the share link generation UI. Also remove the factoryId guard from
generateShortLink since it only needs planId and factoryType.

Co-Authored-By: Claude <noreply@anthropic.com>

src/components/plans/ShareModal.tsx

@@ -75,7 +75,14 @@ export function ShareModal({
   // 获取当前用户的公司名称和检查合作关系
   useEffect(() => {
     const fetchData = async () => {
-      if (!isOpen || !factoryId) return;
+      if (!isOpen) return;
+
+      // No factoryId means unlinked plan — skip relationship check, go straight to share link
+      if (!factoryId) {
+        setHasRelationship(false);
+        setIsCheckingRelationship(false);
+        return;
+      }
 
       setIsCheckingRelationship(true);
 
@@ -132,8 +139,6 @@ export function ShareModal({
 
   // 生成短链（30分钟有效）
   const generateShortLink = useCallback(async () => {
-    if (!factoryId) return;
-
     setIsGeneratingLink(true);
 
     try {