feat(servers): 凭据轮询登录与连接失败列表

- 密码/SSH密钥预设增加用户名；快速添加(IP)轮询全部预设尝试 SSH 登录
- 成功入 servers 列表；失败写入 pending_servers 并支持重试/删除
- 新增 credential_poller、try_ssh_login 与 add-by-ip/pending API

server/api/settings.py

@@ -491,7 +491,10 @@ async def list_presets(admin: Admin = Depends(get_current_admin), db: AsyncSessi
     """List all password presets"""
     repo = PasswordPresetRepositoryImpl(db)
     presets = await repo.get_all()
-    return [{"id": p.id, "name": p.name, "created_at": str(p.created_at)} for p in presets]
+    return [
+        {"id": p.id, "name": p.name, "username": p.username or "root", "created_at": str(p.created_at)}
+        for p in presets
+    ]
 
 
 @preset_router.post("/", response_model=dict, status_code=201)
@@ -505,7 +508,11 @@ async def create_preset(
     from server.infrastructure.database.crypto import encrypt_value
     repo = PasswordPresetRepositoryImpl(db)
     encrypted = encrypt_value(payload.encrypted_pw)
-    preset = PasswordPreset(name=payload.name, encrypted_pw=encrypted)
+    preset = PasswordPreset(
+        name=payload.name,
+        username=(payload.username or "root").strip() or "root",
+        encrypted_pw=encrypted,
+    )
     created = await repo.create(preset)
 
     audit_repo = AuditLogRepositoryImpl(db)
@@ -541,6 +548,8 @@ async def update_preset(
     new_pw = updates.pop("encrypted_pw", None)
     if updates.get("name"):
         preset.name = updates["name"]
+    if updates.get("username"):
+        preset.username = updates["username"].strip() or "root"
     if new_pw:
         preset.encrypted_pw = encrypt_value(new_pw)
 
@@ -625,7 +634,16 @@ async def list_ssh_key_presets(admin: Admin = Depends(get_current_admin), db: As
     """List all SSH key presets"""
     repo = SshKeyPresetRepositoryImpl(db)
     presets = await repo.get_all()
-    return [{"id": p.id, "name": p.name, "public_key": p.public_key or "", "created_at": str(p.created_at)} for p in presets]
+    return [
+        {
+            "id": p.id,
+            "name": p.name,
+            "username": p.username or "root",
+            "public_key": p.public_key or "",
+            "created_at": str(p.created_at),
+        }
+        for p in presets
+    ]
 
 
 @ssh_key_preset_router.post("/", response_model=dict, status_code=201)
@@ -639,7 +657,12 @@ async def create_ssh_key_preset(
     from server.infrastructure.database.crypto import encrypt_value
     repo = SshKeyPresetRepositoryImpl(db)
     encrypted_private = encrypt_value(payload.private_key)
-    preset = SshKeyPreset(name=payload.name, encrypted_private_key=encrypted_private, public_key=payload.public_key)
+    preset = SshKeyPreset(
+        name=payload.name,
+        username=(payload.username or "root").strip() or "root",
+        encrypted_private_key=encrypted_private,
+        public_key=payload.public_key,
+    )
     created = await repo.create(preset)
 
     audit_repo = AuditLogRepositoryImpl(db)
@@ -675,6 +698,8 @@ async def update_ssh_key_preset(
     new_private_key = updates.pop("private_key", None)
     if updates.get("name"):
         preset.name = updates["name"]
+    if updates.get("username"):
+        preset.username = updates["username"].strip() or "root"
     if new_private_key:
         preset.encrypted_private_key = encrypt_value(new_private_key)
     if "public_key" in updates: