feat(app): add drag-and-drop file upload and file picker to composer (#1474)

- Desktop web: drag-and-drop non-image files onto the chat pane to upload
- Desktop web: file picker option in the composer attachment sheet
- Uploaded files are sent to the LLM as filename references in a tmp directory
- New useFilePicker hook for cross-platform file picking
- Extended useFileDropZone to support generic file drops
- Added UploadedFileAttachment type to protocol and composer attachment system
- Fixed adaptive modal sheet closing on backdrop press in selection mode

packages/app/src/i18n/resources/fr.ts

@@ -100,12 +100,15 @@ export const fr: TranslationResources = {
     },
     attachments: {
       addImage: "Ajouter une image",
+      addFile: "Upload file",
       addIssueOrPr: "Ajouter un problème ouPR",
       dropImagesHere: "Déposez des images ici",
+      dropFilesHere: "Drop files here",
       editQueuedMessage: "Modifier le message en file d'attente",
       sendQueuedMessageNow: "Envoyer le message en file d'attente maintenant",
       openImage: "Ouvrir la pièce jointe de l'image",
       removeImage: "Supprimer l'image jointe",
+      removeFile: "Remove file attachment",
       openGithub: "Ouvrir{{kind}}#{{number}}",
       removeGithub: "Supprimer{{kind}}#{{number}}",
       browserElement: "Élément ·{{tag}}",
@@ -120,6 +123,8 @@ export const fr: TranslationResources = {
       noHostSelected: "Aucun hôte sélectionné",
       initialPromptRequired: "Une invite initiale est requise",
       alreadyLoading: "Déjà en cours de chargement",
+      uploadFailed: "Failed to upload file",
+      fileTooLarge: "{{fileName}} is too large (max {{size}})",
     },
     clientCommands: {
       archiveAgent: "Archiver l'agent actuel",