fix: 前缀全部加连字符，与 thinking_protocol.go 风格对齐

deepseek → deepseek-、moonshot → moonshot-、qwen → qwen-/qwen2-/qwen3-/qwen4-、
minimax → minimax-、llama → llama-/llama2-/llama3-、mistral → mistral-、
mixtral → mixtral-。避免无连字符前缀误伤假想的连写模型名。

backend/internal/service/openai_model_mapping.go

@@ -29,23 +29,28 @@ func resolveOpenAIForwardModel(account *Account, requestedModel, defaultMappedMo
 // （调度过滤看到的是改写前的原始模型名）。前缀分类的先例见
 // ResolveThinkingProtocol（thinking_protocol.go）。
 var openAIOAuthForeignModelPrefixes = []string{
-	"deepseek",
+	"deepseek-",
 	"glm-",
 	"kimi-",
-	"moonshot",
-	"qwen",
+	"moonshot-",
+	"qwen-",
+	"qwen2-",
+	"qwen3-",
+	"qwen4-",
 	"qwq-",
-	"minimax",
+	"minimax-",
 	"gemini-",
 	"gemma-",
 	"grok-",
 	"doubao-",
 	"hunyuan-",
-	"llama",
+	"llama-",
+	"llama2-",
+	"llama3-",
 	"meta-llama",
-	"mistral",
-	"mixtral",
-	"baichuan",
+	"mistral-",
+	"mixtral-",
+	"baichuan-",
 	"ernie-",
 	"step-",
 	"seed-",

backend/internal/service/openai_oauth_model_support_test.go

@@ -106,4 +106,5 @@ func TestIsOpenAIOAuthServableModel(t *testing.T) {
 	require.True(t, isOpenAIOAuthServableModel("DeepThink-x"))  // 非黑名单前缀，保持允许
 	require.False(t, isOpenAIOAuthServableModel("DeepSeek-V4")) // 大小写不敏感
 	require.False(t, isOpenAIOAuthServableModel("qwen3-235b-thinking"))
+	require.True(t, isOpenAIOAuthServableModel("deepseekcoder")) // 无连字符 → 非黑名单前缀，保持允许
 }