feat(eo): restore audioBase64 mode for Gemini batch transcription

- POST /corrections/eo accepts audioBase64 + mimeType (XOR with transcript)
- Gemini transcribeAudio called server-side before correction
- No audio storage (client downloads locally)
- /transcriptions/token kept for future Deepgram live use

Typecheck: OK · Tests: all green

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/routes/__tests__/correctionsEO.test.ts

@@ -73,7 +73,7 @@ describe("POST /corrections/eo — Sprint 4a", () => {
     expect(res.status).toBe(400);
   });
 
-  it("400 si transcript manquant", async () => {
+  it("400 si ni transcript ni audioBase64 fournis", async () => {
     const app = buildApp();
     const res = await app.request("/corrections/eo", {
       method: "POST",
@@ -85,6 +85,36 @@ describe("POST /corrections/eo — Sprint 4a", () => {
     expect(body.code).toBe("VALIDATION_ERROR");
   });
 
+  it("400 si transcript ET audioBase64 fournis simultanément (XOR)", async () => {
+    const app = buildApp();
+    const res = await app.request("/corrections/eo", {
+      method: "POST",
+      headers: JSON_HEADERS,
+      body: JSON.stringify({
+        simulationId: "s1",
+        tache: "EO_T1",
+        transcript: "t",
+        audioBase64: "AAAA",
+        mimeType: "audio/webm",
+      }),
+    });
+    expect(res.status).toBe(400);
+  });
+
+  it("400 si audioBase64 sans mimeType", async () => {
+    const app = buildApp();
+    const res = await app.request("/corrections/eo", {
+      method: "POST",
+      headers: JSON_HEADERS,
+      body: JSON.stringify({
+        simulationId: "s1",
+        tache: "EO_T1",
+        audioBase64: "AAAA",
+      }),
+    });
+    expect(res.status).toBe(400);
+  });
+
   it("400 si nclc_cible invalide", async () => {
     const app = buildApp();
     const res = await app.request("/corrections/eo", {
@@ -133,6 +163,34 @@ describe("POST /corrections/eo — Sprint 4a", () => {
     );
   });
 
+  it("200 mode batch audio (transmet audioBase64 + mimeType au controller)", async () => {
+    correctEOMock.mockResolvedValue({
+      data: { score: 14, nclc: 9, simulation_id: "s-audio", diagnostic: "d" },
+    });
+    const app = buildApp();
+    const res = await app.request("/corrections/eo", {
+      method: "POST",
+      headers: JSON_HEADERS,
+      body: JSON.stringify({
+        simulationId: "s-audio",
+        tache: "EO_T1",
+        audioBase64: "AAAA",
+        mimeType: "audio/webm",
+      }),
+    });
+    expect(res.status).toBe(200);
+    expect(correctEOMock).toHaveBeenCalledWith(
+      expect.objectContaining({
+        simulationId: "s-audio",
+        tache: "EO_T1",
+        nclcCible: 9,
+        audioBase64: "AAAA",
+        mimeType: "audio/webm",
+      }),
+      expect.any(Object),
+    );
+  });
+
   it("200 avec nclc_cible=10 transmis au controller", async () => {
     correctEOMock.mockResolvedValue({
       data: { score: 16, nclc: 10, simulation_id: "s2", diagnostic: "d" },