feat(home): add AI story expand button and modal

messages/en/home.json

@@ -11,5 +11,15 @@
     "minutesAgo": "{n}m ago",
     "hoursAgo": "{n}h ago",
     "daysAgo": "{n}d ago"
+  },
+  "aiWrite": {
+    "trigger": "AI Write",
+    "modalTitle": "AI Writing Assistant",
+    "modalSubtitle": "Enter your idea and let AI generate a complete story",
+    "inputLabel": "Enter your creative idea",
+    "placeholder": "Enter keywords, story outline, or a short idea...\n\ne.g.\n• ancient palace, revenge, mystery, female lead\n• Act 1: The heroine returns to the capital; Act 2: A chance encounter at the royal banquet",
+    "hint": "💡 You can enter keywords, story outlines, or creative descriptions. AI will expand your input into a complete story",
+    "startAiWrite": "Start AI Writing",
+    "cancel": "Cancel"
   }
 }

messages/en/progress.json

@@ -65,6 +65,7 @@
     "screenplayConvert": "Screenplay conversion",
     "voiceAnalyze": "Voice line analysis",
     "analyzeGlobal": "Global analysis",
+    "aiStoryExpand": "AI story expansion",
     "aiModifyAppearance": "Character description modify",
     "aiModifyLocation": "Location description modify",
     "aiModifyShotPrompt": "Shot prompt modify",
@@ -104,6 +105,8 @@
     "scriptToStoryboardStep": "Execute script-to-storyboard step",
     "scriptToStoryboardPersist": "Persist script-to-storyboard output",
     "scriptToStoryboardPersistDone": "Storyboard and voice output persisted",
+    "aiStoryExpandPrepare": "Prepare AI story expansion",
+    "aiStoryExpandDone": "AI story expansion completed",
     "insertPanelGenerateText": "Generate inserted panel text",
     "insertPanelPersist": "Persist inserted panel",
     "pollingExternal": "Waiting for external service",