feat: switch AI provider from Anthropic to DeepSeek

- lib/claude/client.ts: replace Anthropic SDK with openai package pointed at DeepSeek baseURL
- 4 AI routes: port tool definitions, tool_choice, and output parsing to OpenAI function-calling format
- Drop thinking:{type:'adaptive'} (no DeepSeek equivalent); model string → deepseek-chat
- settings/route.ts: add DEEPSEEK_API_KEY to ALLOWED_KEYS
- migration: seed DEEPSEEK_API_KEY placeholder row in app_settings
- tests: update 3 AI route tests to mock createDeepSeekClient + OpenAI response shape

Voyage AI embedding path untouched (DeepSeek has no embeddings endpoint).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CPf5Rc8QPx6V8KLEEgfKEQ

tests/api/incidents/triage-suggest.test.ts

@@ -9,6 +9,15 @@ const mockIncident = {
   medical_status: 'medical_treatment',
 }
 
+const triageOutput = {
+  severity: 3,
+  is_fatality: false,
+  is_serious_bodily_injury: true,
+  is_dangerous_occurrence: false,
+  is_occupational_disease: false,
+  rationale: 'Fracture constitutes serious bodily injury under NADOPOD 2004.',
+}
+
 vi.mock('@/lib/supabase/server', () => ({
   createClient: vi.fn().mockResolvedValue({
     auth: {
@@ -17,6 +26,7 @@ vi.mock('@/lib/supabase/server', () => ({
     from: vi.fn().mockReturnValue({
       select: vi.fn().mockReturnThis(),
       eq: vi.fn().mockReturnThis(),
+      gte: vi.fn().mockResolvedValue({ count: 0 }),
       single: vi.fn()
         .mockResolvedValueOnce({ data: { role: 'hse' } }) // profile
         .mockResolvedValueOnce({ data: mockIncident }),    // incident
@@ -26,22 +36,23 @@ vi.mock('@/lib/supabase/server', () => ({
 }))
 
 vi.mock('@/lib/claude/client', () => ({
-  createAnthropicClient: vi.fn().mockReturnValue({
-    messages: {
-      create: vi.fn().mockResolvedValue({
-        content: [{
-          type: 'tool_use',
-          name: 'suggest_triage',
-          input: {
-            severity: 3,
-            is_fatality: false,
-            is_serious_bodily_injury: true,
-            is_dangerous_occurrence: false,
-            is_occupational_disease: false,
-            rationale: 'Fracture constitutes serious bodily injury under NADOPOD 2004.',
-          },
-        }],
-      }),
+  createDeepSeekClient: vi.fn().mockReturnValue({
+    chat: {
+      completions: {
+        create: vi.fn().mockResolvedValue({
+          choices: [{
+            message: {
+              tool_calls: [{
+                type: 'function',
+                function: {
+                  name: 'suggest_triage',
+                  arguments: JSON.stringify(triageOutput),
+                },
+              }],
+            },
+          }],
+        }),
+      },
     },
   }),
 }))