fix: 三平台内容差异化 + admin敏感词管理表格化

- writer.py: _expand_section() 去除 <100字阈值，始终调用 LLM 平台专属扩写
- prompt_loader.py: 新增 section_expansion_zhihu/wechat/xiaohongshu 三个独立 prompt
- admin.html: 配置管理标签页 + 敏感词/清理规则子标签 + 敏感词表格化管理(编辑/删除)
- config_items.py: PUT /sensitive-words/{id} 支持更新 word/category
- compliance_checker.py: AI 套话从 DB 加载 + 人称规则修正
- initial_data.py: PlatformConfig 字数迁移 + 新种子
- 各前端页面: LLM 配置 rate_limit 字段 + 供应商列表排序

platform/backend/app/initial_data.py

@@ -35,14 +35,26 @@ def import_initial_data():
             db.commit()
             print(f"✅ 创建默认管理员: {DEFAULT_ADMIN_USERNAME}")
 
-        # 补充或更新 LLM 供应商配置（nvidia 为主，opencode-go 为备）
+        # 补充或更新 LLM 供应商配置（nvidia 为主，sensenova 为备，含多模型）
         expected = {
             "opencode-go": dict(provider="opencode-go", model="deepseek-v4-flash",
                 base_url="https://opencode.ai/zen/go/v1", temperature=0.7, max_tokens=131072, is_active=True,
                 user_prompt_template="将以下内容扩展为完整文章：\n{topic_title}\n{core_concept}"),
-            "nvidia": dict(provider="nvidia", model="stepfun-ai/step-3.5-flash",
+            "nvidia": dict(provider="nvidia", model="qwen/qwen3.5-397b-a17b",
                 base_url="https://integrate.api.nvidia.com/v1", temperature=0.5, max_tokens=131072, is_active=False,
                 user_prompt_template="将以下内容扩展为完整章节：\n{section_content}"),
+            "sensenova-6.7-flash-lite": dict(provider="sensenova", model="sensenova-6.7-flash-lite",
+                base_url="https://token.sensenova.cn/v1", temperature=0.3, max_tokens=16384, is_active=True,
+                rate_limit=1500, rate_limit_window_minutes=300,
+                user_prompt_template="将以下内容扩展为完整章节：\n{section_content}"),
+            "sensenova-u1-fast": dict(provider="sensenova", model="sensenova-u1-fast",
+                base_url="https://token.sensenova.cn/v1", temperature=0.3, max_tokens=16384, is_active=True,
+                rate_limit=1500, rate_limit_window_minutes=300,
+                user_prompt_template="根据以下内容生成信息图：\n{section_content}"),
+            "sensenova-deepseek": dict(provider="sensenova", model="deepseek-v4-flash",
+                base_url="https://token.sensenova.cn/v1", temperature=0.3, max_tokens=16384, is_active=True,
+                rate_limit=500, rate_limit_window_minutes=300,
+                user_prompt_template="将以下内容扩展为完整章节：\n{section_content}"),
         }
         existing = {c.name: c for c in db.query(LLMConfig).all()}
         for name, cfg in expected.items():
@@ -90,7 +102,7 @@ def import_initial_data():
                     "platform": "zhihu",
                     "name": "知乎",
                     "icon": "🔍",
-                    "default_format": "长文深度分析，1500-3000字，有数据支撑",
+                    "default_format": "深度分析 3000-8000字，数据驱动",
                     "compliance_rules": {
                         "max_title_len": 100,
                         "allowed_tags": ["科技", "生活", "职场", "教育", "可持续", "AI", "远程工作", "个人成长"],
@@ -102,14 +114,14 @@ def import_initial_data():
                     "image_count_max": 0,
                     "image_width": 0,
                     "image_height": 0,
-                    "min_words": 1500,
-                    "max_words": 3000
+                    "min_words": 3000,
+                    "max_words": 8000
                 },
                 {
                     "platform": "wechat",
                     "name": "微信公众号",
                     "icon": "💚",
-                    "default_format": "公众号图文，800-1500字，亲切口语化",
+                    "default_format": "个人叙事 2000-4000字，对话感",
                     "compliance_rules": {
                         "max_title_len": 32,
                         "allowed_tags": ["科技", "生活", "职场", "教育", "可持续", "AI", "远程工作", "个人成长"],
@@ -121,14 +133,14 @@ def import_initial_data():
                     "image_count_max": 3,
                     "image_width": 1080,
                     "image_height": 1080,
-                    "min_words": 800,
-                    "max_words": 1500
+                    "min_words": 2000,
+                    "max_words": 4000
                 },
                 {
                     "platform": "xiaohongshu",
                     "name": "小红书",
                     "icon": "📕",
-                    "default_format": "图文笔记，300-800字，emoji+标签",
+                    "default_format": "精炼干货 400-1000字，实用优先",
                     "compliance_rules": {
                         "max_title_len": 50,
                         "allowed_tags": ["生活方式", "可持续", "AI", "个人成长", "极简", "环保"],
@@ -140,14 +152,29 @@ def import_initial_data():
                     "image_count_max": 6,
                     "image_width": 1080,
                     "image_height": 1440,
-                    "min_words": 300,
-                    "max_words": 800
+                    "min_words": 400,
+                    "max_words": 1000
                 }
             ]
             for p in platforms:
                 db.add(PlatformConfig(**p))
             db.commit()
             print("✅ 插入平台配置")
+        else:
+            # 更新已有平台配置的字数要求（迁移：2026-06 内容质量升级）
+            platform_updates = {
+                "zhihu": {"min_words": 3000, "max_words": 8000, "default_format": "深度分析 3000-8000字，数据驱动"},
+                "wechat": {"min_words": 2000, "max_words": 4000, "default_format": "个人叙事 2000-4000字，对话感"},
+                "xiaohongshu": {"min_words": 400, "max_words": 1000, "default_format": "精炼干货 400-1000字，实用优先"},
+            }
+            for p in db.query(PlatformConfig).all():
+                if p.platform in platform_updates:
+                    up = platform_updates[p.platform]
+                    p.min_words = up["min_words"]
+                    p.max_words = up["max_words"]
+                    p.default_format = up["default_format"]
+            db.commit()
+            print("✅ 平台配置已更新（字数/格式）")
 
         if db.query(TopicField).count() == 0:
             fields = [