feat: migrate AI to Vercel AI SDK, add OpenAI provider, fix worklist

- Replace raw @anthropic-ai/sdk with Vercel AI SDK (generateText, tool, generateObject)
- Add provider abstraction (ai-provider.ts) — swap OpenAI/Anthropic via env var
- AI chat controller: dynamic KB from platform (clinics, packages, insurance), zero hardcoding
- AI enrichment service: use generateObject with Zod schema instead of manual JSON parsing
- Worklist: resolve agent name from platform currentUser API instead of JWT decode
- Worklist: fix GraphQL field names to match platform remapping (source, status, direction, etc.)
- Config: add AI_PROVIDER, AI_MODEL, OPENAI_API_KEY env vars

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/ai/ai-provider.ts

@@ -0,0 +1,26 @@
+import { ConfigService } from '@nestjs/config';
+import { anthropic } from '@ai-sdk/anthropic';
+import { openai } from '@ai-sdk/openai';
+import type { LanguageModel } from 'ai';
+
+export function createAiModel(config: ConfigService): LanguageModel | null {
+    const provider = config.get<string>('ai.provider') ?? 'openai';
+    const model = config.get<string>('ai.model') ?? 'gpt-4o-mini';
+
+    if (provider === 'anthropic') {
+        const apiKey = config.get<string>('ai.anthropicApiKey');
+        if (!apiKey) return null;
+        return anthropic(model);
+    }
+
+    // Default to openai
+    const apiKey = config.get<string>('ai.openaiApiKey');
+    if (!apiKey) return null;
+    return openai(model);
+}
+
+export function isAiConfigured(config: ConfigService): boolean {
+    const provider = config.get<string>('ai.provider') ?? 'openai';
+    if (provider === 'anthropic') return !!config.get<string>('ai.anthropicApiKey');
+    return !!config.get<string>('ai.openaiApiKey');
+}