chore: opencode冗余清理 + LLM任务级模型选择 + systemd服务化

- 删除 opencode_search.py / mcp_search_server.py 及所有 MCP 引用
- 移除搜索缓存定时任务（scheduled_refresh_search_cache）
- 清理前后端所有 opencode/MCP 代码和注释
- LLM 提供商量换：opencode-go→nvidia(默认)+sensenova(合规审查)
- llm_configs 新增 is_default 字段，API 层互斥逻辑
- 所有定时任务支持独立 LLM 模型选择（LLM_TASK_PROVIDER env）
- compliance_optimizer.py 修复：import os / 解硬编码 / 关键词过滤
- Scheduler 日志修复：始终 INSERT，避免僵尸 running 行
- Systemd 服务化：Restart=always / 单 worker / Type=exec
- 搜索提供商：替换 opencode→360/搜狗/微信（免 Key）
- 更新 AGENTS.md / PROGRESS.md

platform/backend/app/api/task_configs.py

@@ -11,14 +11,13 @@ from .auth import get_current_admin
 router = APIRouter(prefix="/api/admin/task-configs", tags=["admin"])
 
 DEFAULT_CONFIGS = {
-    "scheduled_refresh_search_cache": {"name": "🔍 搜索缓存", "cron": "01:00", "params": {}},
-    "scheduled_fetch_trends": {"name": "🔥 热点趋势", "cron": "01:10", "params": {}},
-    "scheduled_collect": {"name": "📡 内容采集", "cron": "01:30", "params": {"max_topics": 20}},
-    "scheduled_generate": {"name": "🤖 内容创作", "cron": "02:00", "params": {"auto_review": True}},
-    "scheduled_optimize": {"name": "🔍 合规审查", "cron": "03:00", "params": {"auto_pass_threshold": 80}},
-    "scheduled_optimize_sources": {"name": "📡 信息源优化", "cron": "05:00", "params": {}},
-    "scheduled_metrics_sync": {"name": "📊 指标同步", "cron": "06:00", "params": {}},
-    "scheduled_task_monitor": {"name": "⏰ 任务监控", "cron": "*", "params": {}},
+    "scheduled_fetch_trends": {"name": "🔥 热点趋势", "cron": "01:10", "params": {"llm_provider": "nvidia"}},
+    "scheduled_collect": {"name": "📡 内容采集", "cron": "01:30", "params": {"max_topics": 20, "llm_provider": "nvidia"}},
+    "scheduled_generate": {"name": "🤖 内容创作", "cron": "02:00", "params": {"auto_review": True, "llm_provider": "nvidia"}},
+    "scheduled_optimize": {"name": "🔍 合规审查", "cron": "03:00", "params": {"auto_pass_threshold": 80, "llm_provider": "sensenova"}},
+    "scheduled_optimize_sources": {"name": "📡 信息源优化", "cron": "05:00", "params": {"llm_provider": "nvidia"}},
+    "scheduled_metrics_sync": {"name": "📊 指标同步", "cron": "06:00", "params": {"llm_provider": "nvidia"}},
+    "scheduled_task_monitor": {"name": "⏰ 任务监控", "cron": "*", "params": {"llm_provider": "nvidia"}},
 }
 
 def _attach_last_log(resp: TaskConfigResponse, db: Session, module_id: str) -> TaskConfigResponse: