fix: correction de toutes les erreurs CI — vet, lint, race detector et config

- clipboard_windows.go: remplacement unsafe.Pointer par unsafe.Add pour go vet 1.26
- clipboard_windows.go: correction errcheck (defer syscall) et ineffassign
- daemon_test.go: mockClipboard thread-safe avec sync.RWMutex (data race)
- daemon_test.go: correction errcheck sur go da.Run()
- server_test.go: vérification des erreurs json.Marshal
- config_test.go: vérification des erreurs MkdirAll/WriteFile
- peers.example.toml: mise à jour au format TOML actuel

internal/server/server_test.go

@@ -29,7 +29,10 @@ func TestHandleClipAcceptsValidPayload(t *testing.T) {
 		Ts:     1690000000000000000,
 		Origin: "other-machine",
 	}
-	body, _ := json.Marshal(payload)
+	body, err := json.Marshal(payload)
+	if err != nil {
+		t.Fatalf("json.Marshal: %v", err)
+	}
 
 	req := httptest.NewRequest(http.MethodPost, "/clip", bytes.NewReader(body))
 	req.Header.Set("Content-Type", "application/json")
@@ -59,7 +62,10 @@ func TestHandleClipIgnoresEcho(t *testing.T) {
 		Ts:     1690000000000000000,
 		Origin: "other-machine",
 	}
-	body, _ := json.Marshal(payload)
+	body, err := json.Marshal(payload)
+	if err != nil {
+		t.Fatalf("json.Marshal: %v", err)
+	}
 
 	req := httptest.NewRequest(http.MethodPost, "/clip", bytes.NewReader(body))
 	w := httptest.NewRecorder()
@@ -100,7 +106,10 @@ func TestHandleClipRejectsEmptyText(t *testing.T) {
 		Ts:     1690000000000000000,
 		Origin: "other-machine",
 	}
-	body, _ := json.Marshal(payload)
+	body, err := json.Marshal(payload)
+	if err != nil {
+		t.Fatalf("json.Marshal: %v", err)
+	}
 
 	req := httptest.NewRequest(http.MethodPost, "/clip", bytes.NewReader(body))
 	w := httptest.NewRecorder()