Update DeepSeek model pricing and add V4 Pro (#938)

Update all DeepSeek model prices to match current V4 Flash pricing
($0.14/$0.28 per 1M input/output tokens), and add V4 Pro model with
its own pricing ($0.435/$0.87). Also add deepseek-v4-pro to the
provider model list.

Co-authored-by: smarthomeblack <truongbber@gmail.com>

open-sse/config/providerModels.js

@@ -415,6 +415,7 @@ export const PROVIDER_MODELS = {
     { id: "gpt-oss-120b-250805", name: "GPT-OSS-120B" },
   ],
   deepseek: [
+    { id: "deepseek-v4-pro", name: "DeepSeek V4 Pro" },
     { id: "deepseek-v4-flash", name: "DeepSeek V4 Flash" },
     { id: "deepseek-chat", name: "DeepSeek V3.2 Chat" },
     { id: "deepseek-reasoner", name: "DeepSeek V3.2 Reasoner" },