Add OpenAI-compatible LLM client service (v0.19.0)

LlmService wraps the local OpenAI-compatible server (default
http://192.168.1.70:1111/v1, no auth) with native fetch only — no new
dependencies. listModels() -> data[].id; chat(messages, opts?) ->
choices[0].message.content (non-2xx throws with status + body snippet);
summarize(text) = chat() with a concise-summary system prompt.

Env: LLM_API_BASE / LLM_MODEL (qwen3.8-27b) / LLM_TIMEOUT_MS (60000,
AbortSignal.timeout). Plain feature module wired into app.module.ts;
docs synced (AGENTS.md, README env list).

src/llm/llm.service.ts

@@ -0,0 +1,68 @@
+import { Injectable } from '@nestjs/common';
+
+/** A single chat message in OpenAI chat-completions shape. */
+export interface ChatMessage {
+  role: string;
+  content: string;
+}
+
+@Injectable()
+export class LlmService {
+  // read at construction, like other services' env config
+  private readonly apiBase =
+    process.env.LLM_API_BASE ?? 'http://192.168.1.70:1111/v1';
+  private readonly model = process.env.LLM_MODEL ?? 'qwen3.8-27b';
+  // local 27B model can be slow — generous default
+  private readonly timeoutMs = parseInt(
+    process.env.LLM_TIMEOUT_MS ?? '60000',
+    10,
+  );
+
+  /** GET {base}/models → the `data[].id` strings. */
+  async listModels(): Promise<string[]> {
+    const res = await fetch(`${this.apiBase}/models`, {
+      signal: AbortSignal.timeout(this.timeoutMs),
+    });
+    if (!res.ok) {
+      throw new Error(
+        `listModels failed: HTTP ${res.status} ${(await res.text()).slice(0, 200)}`,
+      );
+    }
+    const body = (await res.json()) as { data?: { id: string }[] };
+    return (body.data ?? []).map((m) => m.id);
+  }
+
+  /** POST {base}/chat/completions → `choices[0].message.content`. */
+  async chat(
+    messages: ChatMessage[],
+    opts?: { maxTokens?: number; temperature?: number },
+  ): Promise<string> {
+    const res = await fetch(`${this.apiBase}/chat/completions`, {
+      method: 'POST',
+      headers: { 'content-type': 'application/json' },
+      body: JSON.stringify({ model: this.model, messages, ...opts }),
+      signal: AbortSignal.timeout(this.timeoutMs),
+    });
+    if (!res.ok) {
+      throw new Error(
+        `chat failed: HTTP ${res.status} ${(await res.text()).slice(0, 200)}`,
+      );
+    }
+    const body = (await res.json()) as {
+      choices?: { message?: { content?: string } }[];
+    };
+    const content = body.choices?.[0]?.message?.content;
+    if (typeof content !== 'string') {
+      throw new Error('chat failed: no choices[0].message.content in response');
+    }
+    return content;
+  }
+
+  /** Thin wrapper over chat(): the stated primary use of this service. */
+  async summarize(text: string): Promise<string> {
+    return this.chat([
+      { role: 'system', content: 'Summarize the following text concisely.' },
+      { role: 'user', content: text },
+    ]);
+  }
+}