Live AI provider/model switching without restart

Backend:
- RuntimeAIConfig singleton: mutable in-memory overrides for provider/model
- PATCH /admin/api/ai/config: change active provider/model on the fly
- GET /admin/api/ai/config: read current runtime state
- ai_vision.py: uses runtime_ai_config before falling back to settings
- health/status endpoints reflect runtime overrides

Frontend:
- 'Définir comme actif' button in AI config section
- Live feedback message on save

imago-admin/src/api/ai.ts

@@ -1,4 +1,4 @@
-import { apiGet, apiPost } from './client';
+import { apiGet, apiPost, apiPatch } from './client';
 import type { AIStatus, TestModelRequest, TestModelResponse } from '@/types/ai.types';
 
 export async function fetchAIStatus(): Promise<AIStatus> {
@@ -8,3 +8,24 @@ export async function fetchAIStatus(): Promise<AIStatus> {
 export async function testModel(body: TestModelRequest): Promise<TestModelResponse> {
     return apiPost<TestModelResponse>('/admin/api/ai/test', body);
 }
+
+export interface UpdateAIConfigRequest {
+    provider?: string;
+    model?: string;
+    reset?: boolean;
+}
+
+export interface UpdateAIConfigResponse {
+    provider: string;
+    model: string;
+    is_overridden: boolean;
+    message: string;
+}
+
+export async function updateAIConfig(body: UpdateAIConfigRequest): Promise<UpdateAIConfigResponse> {
+    return apiPatch<UpdateAIConfigResponse>('/admin/api/ai/config', body);
+}
+
+export async function fetchRuntimeConfig(): Promise<UpdateAIConfigResponse> {
+    return apiGet<UpdateAIConfigResponse>('/admin/api/ai/config');
+}

imago-admin/src/components/admin/AIConfigSection.tsx

@@ -1,6 +1,6 @@
 import { useState, useEffect, useCallback } from 'react';
 import { useQuery } from '@tanstack/react-query';
-import { fetchAIStatus, testModel } from '@/api/ai';
+import { fetchAIStatus, testModel, updateAIConfig } from '@/api/ai';
 import type { TestModelResponse } from '@/types/ai.types';
 import { Bot, Zap, AlertTriangle, CheckCircle, Loader2, RefreshCw, Cpu, ChevronDown } from 'lucide-react';
 import { clsx } from 'clsx';
@@ -18,6 +18,8 @@ export function AIConfigSection() {
     const [testResult, setTestResult] = useState<TestModelResponse | null>(null);
     const [isTesting, setIsTesting] = useState(false);
     const [testError, setTestError] = useState<string | null>(null);
+    const [isSaving, setIsSaving] = useState(false);
+    const [saveMessage, setSaveMessage] = useState<string | null>(null);
 
     // Sync dropdowns with current config when data loads
     useEffect(() => {
@@ -64,6 +66,26 @@ export function AIConfigSection() {
         }
     }, [selectedProvider, selectedModel]);
 
+    const handleSetActive = useCallback(async () => {
+        if (!selectedProvider || !selectedModel) return;
+
+        setIsSaving(true);
+        setSaveMessage(null);
+        try {
+            const result = await updateAIConfig({
+                provider: selectedProvider,
+                model: selectedModel,
+            });
+            setSaveMessage(result.message);
+            // Auto-clear message after 4s
+            setTimeout(() => setSaveMessage(null), 4000);
+        } catch (err: any) {
+            setSaveMessage(err?.message || 'Erreur lors de la mise à jour');
+        } finally {
+            setIsSaving(false);
+        }
+    }, [selectedProvider, selectedModel]);
+
     if (isLoading) {
         return (
             <section className="card mb-6">
@@ -240,6 +262,30 @@ export function AIConfigSection() {
                     )}
                 </button>
 
+                <button
+                    onClick={handleSetActive}
+                    disabled={isSaving || !selectedProvider || !selectedModel}
+                    className="btn-secondary flex items-center gap-2 text-sm disabled:opacity-50 ml-3"
+                >
+                    {isSaving ? (
+                        <>
+                            <Loader2 size={14} className="animate-spin" />
+                            Application...
+                        </>
+                    ) : (
+                        <>
+                            <CheckCircle size={14} />
+                            Définir comme actif
+                        </>
+                    )}
+                </button>
+
+                {saveMessage && (
+                    <span className="ml-3 text-sm text-status-ok animate-fade-in">
+                        {saveMessage}
+                    </span>
+                )}
+
                 {/* Test result — live, no refresh needed */}
                 {(testResult || testError || isTesting) && (
                     <div className={clsx(