fix(dsfr): Modal avec overlay visible et fermeture fiable

L'ancienne implémentation (<dialog> plein écran transparent) rendait la page
inutilisable au clic sur éditer/supprimer : overlay invisible captant tous les
clics, sans fond assombri ni fermeture au clic extérieur. Remplacé par un
overlay React maîtrisé (fond assombri, clic extérieur/Échap/bouton ferment).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/components/ui/Modal.tsx

@@ -12,11 +12,10 @@ interface ModalProps {
   size?: ModalSize;
 }
 
-// Largeur de la colonne DSFR selon la taille demandée.
-const sizeColClasses: Record<ModalSize, string> = {
-  sm: "fr-col-12 fr-col-md-4",
-  md: "fr-col-12 fr-col-md-6",
-  lg: "fr-col-12 fr-col-md-8",
+const maxWidthBySize: Record<ModalSize, string> = {
+  sm: "480px",
+  md: "672px",
+  lg: "896px",
 };
 
 export default function Modal({
@@ -34,10 +33,9 @@ export default function Modal({
   );
 
   useEffect(() => {
-    if (isOpen) {
-      document.addEventListener("keydown", handleKeyDown);
-      document.body.style.overflow = "hidden";
-    }
+    if (!isOpen) return;
+    document.addEventListener("keydown", handleKeyDown);
+    document.body.style.overflow = "hidden";
     return () => {
       document.removeEventListener("keydown", handleKeyDown);
       document.body.style.overflow = "";
@@ -46,49 +44,52 @@ export default function Modal({
 
   if (!isOpen) return null;
 
-  // L'ouverture/fermeture est pilotée par React (isOpen/onClose), on applique
-  // donc la structure et les classes visuelles DSFR sans le JS d'ouverture DSFR.
+  // Overlay React maîtrisé (pas le JS DSFR) : fond assombri visible, fermeture
+  // au clic extérieur / Échap / bouton. Look DSFR via les classes fr-modal__*.
   return (
-    <dialog
-      className="fr-modal fr-modal--opened"
-      aria-modal="true"
+    <div
       role="dialog"
-      open
+      aria-modal="true"
+      onClick={onClose}
       style={{
         position: "fixed",
         inset: 0,
         zIndex: 1000,
-        display: "block",
-        background: "transparent",
-        border: "none",
-        maxWidth: "none",
-        maxHeight: "none",
-        width: "100%",
-        height: "100%",
+        display: "flex",
+        alignItems: "flex-start",
+        justifyContent: "center",
+        overflowY: "auto",
+        padding: "2rem 1rem",
+        background: "rgba(22, 22, 22, 0.64)",
       }}
     >
-      <div className="fr-container fr-container--fluid fr-container-md">
-        <div className="fr-grid-row fr-grid-row--center">
-          <div className={sizeColClasses[size]}>
-            <div className="fr-modal__body">
-              <div className="fr-modal__header">
-                <button
-                  type="button"
-                  className="fr-btn--close fr-btn"
-                  aria-label="Fermer"
-                  onClick={onClose}
-                >
-                  Fermer
-                </button>
-              </div>
-              <div className="fr-modal__content">
-                {title && <h1 className="fr-modal__title">{title}</h1>}
-                {children}
-              </div>
-            </div>
-          </div>
+      <div
+        className="fr-modal__body"
+        onClick={(e) => e.stopPropagation()}
+        style={{
+          width: "100%",
+          maxWidth: maxWidthBySize[size],
+          background: "var(--background-default-grey, #fff)",
+          borderRadius: "0.25rem",
+          boxShadow: "0 8px 24px rgba(0, 0, 0, 0.32)",
+          padding: "1.5rem",
+        }}
+      >
+        <div className="fr-modal__header">
+          <button
+            type="button"
+            className="fr-btn--close fr-btn"
+            aria-label="Fermer"
+            onClick={onClose}
+          >
+            Fermer
+          </button>
+        </div>
+        <div className="fr-modal__content">
+          {title && <h1 className="fr-modal__title">{title}</h1>}
+          {children}
         </div>
       </div>
-    </dialog>
+    </div>
   );
 }