fix: replace SHA comparison with file size for LFS compatibility + add NoChangesModal

Git LFS stores pointer files whose SHA differs from the actual blob SHA,
causing false-positive diffs on every upload. Switching to file size
comparison resolves this for LFS-enabled repos.

Also replaces the inline error message with a dedicated NoChangesModal
when no differences are detected, offering cancel (reset) or modify
(close modal) actions.

components/UploadZone.tsx

@@ -13,22 +13,7 @@ import FolderDropzone from './upload/FolderDropzone'
 import FolderCard from './upload/FolderCard'
 import ActionButtons from './upload/ActionButtons'
 import OverwriteConfirmModal from './upload/OverwriteConfirmModal'
-
-// ---------------------------------------------------------------------------
-// Client-side SHA computation (same as `git hash-object`)
-// ---------------------------------------------------------------------------
-
-async function computeGitBlobSha(file: File): Promise<string> {
-  const buffer = await file.arrayBuffer()
-  const content = new Uint8Array(buffer)
-  const header = new TextEncoder().encode(`blob ${content.length}\0`)
-  const store = new Uint8Array(header.length + content.length)
-  store.set(header)
-  store.set(content, header.length)
-  const hashBuffer = await crypto.subtle.digest('SHA-1', store)
-  const hashArray = Array.from(new Uint8Array(hashBuffer))
-  return hashArray.map((b) => b.toString(16).padStart(2, '0')).join('')
-}
+import NoChangesModal from './upload/NoChangesModal'
 
 // ---------------------------------------------------------------------------
 // API helpers
@@ -56,18 +41,19 @@ async function checkFolderDiffs(
       return { exists: false, diffs: [] }
     }
 
-    const remoteFiles: { name: string; sha: string }[] = data.files || []
-    const remoteMap = new Map(remoteFiles.map((f) => [f.name.toLowerCase(), f.sha]))
+    const remoteFiles: { name: string; size: number }[] = data.files || []
+    const remoteMap = new Map(remoteFiles.map((f) => [f.name.toLowerCase(), f.size]))
 
-    const localFiles: { name: string; sha: string }[] = []
+    // Build local file list with sizes
+    const localFiles: { name: string; size: number }[] = []
     localFiles.push({
       name: folder.modelFile.name,
-      sha: await computeGitBlobSha(folder.modelFile),
+      size: folder.modelFile.size,
     })
     for (const tex of folder.textures) {
       localFiles.push({
         name: tex.name,
-        sha: await computeGitBlobSha(tex.file),
+        size: tex.file.size,
       })
     }
 
@@ -77,10 +63,10 @@ async function checkFolderDiffs(
     for (const local of localFiles) {
       const key = local.name.toLowerCase()
       localNames.add(key)
-      const remoteSha = remoteMap.get(key)
-      if (!remoteSha) {
+      const remoteSize = remoteMap.get(key)
+      if (remoteSize === undefined) {
         diffs.push({ name: local.name, status: 'new' })
-      } else if (remoteSha !== local.sha) {
+      } else if (remoteSize !== local.size) {
         diffs.push({ name: local.name, status: 'changed' })
       }
     }
@@ -177,6 +163,7 @@ export default function UploadZone() {
     folderName: string
     diffs: FileDiff[]
   } | null>(null)
+  const [noChangesFolder, setNoChangesFolder] = useState<string | null>(null)
   const abortRef = useRef<AbortController | null>(null)
 
   // -- Handlers --
@@ -207,7 +194,7 @@ export default function UploadZone() {
     const check = await checkFolderDiffs(folder, destination, secret, abortRef.current?.signal)
     if (check.exists) {
       if (check.diffs.length === 0) {
-        setGlobalError('Aucun fichier modifie — le dossier distant est identique.')
+        setNoChangesFolder(folder.folderName)
         return
       }
       setOverwriteConfirm({ folderName: folder.folderName, diffs: check.diffs })
@@ -330,6 +317,18 @@ export default function UploadZone() {
           onConfirm={proceedUpload}
         />
       )}
+
+      {noChangesFolder && (
+        <NoChangesModal
+          destination={destination}
+          folderName={noChangesFolder}
+          onCancel={() => {
+            setNoChangesFolder(null)
+            handleReset()
+          }}
+          onModify={() => setNoChangesFolder(null)}
+        />
+      )}
     </div>
   )
 }