Replace RSC streaming with /api/ai Route Handler for Docker reliability.

Server Actions + createStreamableValue kept failing in production; fetch-based text stream avoids RSC serialization issues and shows readable error messages.

Co-authored-by: Cursor <cursoragent@cursor.com>

lib/ai/config.ts

@@ -0,0 +1,21 @@
+export function getOpenAiBaseUrl(): string {
+  return (
+    process.env.OPENAI_BASE_URL ??
+    process.env.OPENAI_API_BASE ??
+    "https://op.bz121.com/v1"
+  );
+}
+
+export function getOpenAiModel(): string {
+  return process.env.OPENAI_MODEL ?? "huihui_ai/gemma-4-abliterated:e4b";
+}
+
+export function getOpenAiApiKey(): string {
+  const apiKey = process.env.OPENAI_API_KEY?.trim();
+  if (!apiKey) {
+    throw new Error(
+      "未配置 OPENAI_API_KEY，请在 .env.local 或 Docker env_file 中设置",
+    );
+  }
+  return apiKey;
+}