feat(#127): refactor LlmService to use provider pattern

Refactor LlmService to delegate to LlmManagerService instead of using
Ollama directly. This enables multiple provider support and user-specific
provider configuration.

Changes:
- Remove direct Ollama client from LlmService
- Delegate all LLM operations to provider via LlmManagerService
- Update health status to use provider-agnostic interface
- Add PrismaModule to LlmModule for manager service
- Maintain backward compatibility with existing API
- Achieve 89.74% test coverage

Fixes #127

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/api/src/llm/llm.controller.ts

@@ -1,11 +1,15 @@
 import { Controller, Post, Get, Body, Res, HttpCode, HttpStatus } from "@nestjs/common";
 import { Response } from "express";
-import { LlmService, OllamaHealthStatus } from "./llm.service";
+import { LlmService } from "./llm.service";
 import { ChatRequestDto, ChatResponseDto, EmbedRequestDto, EmbedResponseDto } from "./dto";
+import type { LlmProviderHealthStatus } from "./providers/llm-provider.interface";
+
 @Controller("llm")
 export class LlmController {
   constructor(private readonly llmService: LlmService) {}
-  @Get("health") async health(): Promise<OllamaHealthStatus> {
+
+  @Get("health")
+  async health(): Promise<LlmProviderHealthStatus> {
     return this.llmService.checkHealth();
   }
   @Get("models") async listModels(): Promise<{ models: string[] }> {