refactor: full codebase audit — extract modules, fix type safety, clean dead code

- Extract API helpers from UploadZone into lib/upload-api.ts (FormData builder, checkFolderDiffs, uploadDrive, uploadGit)
- Extract upload orchestration into hooks/useUploadOrchestrator.ts (UploadZone: 489 → 162 lines)
- Extract file diff classification into lib/diff-files.ts (from git route)
- Extract shared SVG icons into components/ui/icons.tsx (7 icons, 0 duplication)
- Extract shared modal wrapper into components/ui/Modal.tsx + ModalActions
- Extract DriveStatusLine sub-component from FolderCard
- Fix checkFolderDiffs silently swallowing auth/network errors (now throws)
- Fix type safety: remove as never casts, add isHttpError type guard, use discriminated union for validateFolder
- Fix nextcloud: cache getConfig, add max bound to findNextVersion, optimize mkdirRecursive (skip PROPFIND)
- Fix drive route: remove req.clone(), extend parseMultiUpload to return extra fields
- Fix commit message: model shown as unchanged with ↔️ on updates (not falsely marked as modified)
- Clean dead code: unused folderExists import, FileStatus/DriveStatus exports, ParsedFile.textureName, getConfig basePath
- Add security headers in next.config.ts (HSTS, X-Content-Type-Options, X-Frame-Options, etc.)
- Update README with new project structure

lib/upload-api.ts

@@ -0,0 +1,182 @@
+// ---------------------------------------------------------------------------
+// Client-side API helpers for upload operations
+// ---------------------------------------------------------------------------
+
+import type { FolderEntry } from './client-types'
+import type { FileDiff } from './types'
+
+export interface CheckResult {
+  exists: boolean
+  diffs: FileDiff[]
+}
+
+// ---------------------------------------------------------------------------
+// Shared FormData builder
+// ---------------------------------------------------------------------------
+
+function buildUploadFormData(
+  folder: FolderEntry,
+  destination: string,
+  extra?: Record<string, string>,
+): FormData {
+  const formData = new FormData()
+  formData.append('folderName', folder.folderName)
+  formData.append('destination', destination)
+
+  if (extra) {
+    for (const [key, value] of Object.entries(extra)) {
+      formData.append(key, value)
+    }
+  }
+
+  formData.append('files', folder.modelFile)
+  formData.append('fileTypes', 'model')
+  formData.append('textureNames', '')
+
+  for (const tex of folder.textures) {
+    formData.append('files', tex.file)
+    formData.append('fileTypes', 'texture')
+    formData.append('textureNames', tex.name)
+  }
+
+  return formData
+}
+
+// ---------------------------------------------------------------------------
+// Check folder diffs against remote (GitHub)
+// ---------------------------------------------------------------------------
+
+/**
+ * Check whether a folder already exists on the remote repo and compute diffs.
+ * Throws on auth/network errors so callers can surface them to the user.
+ */
+export async function checkFolderDiffs(
+  folder: FolderEntry,
+  destination: string,
+  secret: string,
+  signal?: AbortSignal,
+): Promise<CheckResult> {
+  const params = new URLSearchParams({ folderName: folder.folderName, destination })
+  const res = await fetch(`/api/upload/check?${params}`, {
+    headers: { 'x-upload-secret': secret.trim() },
+    signal,
+  })
+
+  const data = await res.json()
+
+  // Surface auth/server errors to the caller
+  if (!res.ok) {
+    throw new Error(data.error || `Erreur serveur (${res.status})`)
+  }
+
+  if (!data.success || !data.exists) {
+    return { exists: false, diffs: [] }
+  }
+
+  const remoteFiles: { name: string; size: number }[] = data.files || []
+  const remoteMap = new Map(remoteFiles.map((f) => [f.name.toLowerCase(), f.size]))
+
+  const diffs: FileDiff[] = []
+  const localNames = new Set<string>()
+
+  // Model: skip size comparison (compression changes the size).
+  const modelKey = folder.modelFile.name.toLowerCase()
+  localNames.add(modelKey)
+  if (!remoteMap.has(modelKey)) {
+    diffs.push({ name: folder.modelFile.name, status: 'new' })
+  }
+
+  // Textures: compare by size
+  for (const tex of folder.textures) {
+    const key = tex.name.toLowerCase()
+    localNames.add(key)
+    const remoteSize = remoteMap.get(key)
+    if (remoteSize === undefined) {
+      diffs.push({ name: tex.name, status: 'new' })
+    } else if (remoteSize !== tex.file.size) {
+      diffs.push({ name: tex.name, status: 'changed' })
+    }
+  }
+
+  // Deleted
+  for (const [name] of remoteMap) {
+    if (!localNames.has(name)) {
+      diffs.push({ name, status: 'deleted' })
+    }
+  }
+
+  return { exists: true, diffs }
+}
+
+// ---------------------------------------------------------------------------
+// Upload original files to Nextcloud Drive
+// ---------------------------------------------------------------------------
+
+/** Upload original files to Nextcloud Drive (no Blender compression). */
+export async function uploadDrive(
+  folder: FolderEntry,
+  secret: string,
+  destination: string,
+  action: 'new' | 'replace',
+  signal?: AbortSignal,
+): Promise<{ success: boolean; error?: string }> {
+  const formData = buildUploadFormData(folder, destination, { action })
+
+  try {
+    const res = await fetch('/api/upload/drive', {
+      method: 'POST',
+      headers: { 'x-upload-secret': secret.trim() },
+      body: formData,
+      signal,
+    })
+    const data = await res.json()
+    if (!data.success) return { success: false, error: data.error }
+    return { success: true }
+  } catch (err) {
+    if (err instanceof DOMException && err.name === 'AbortError') {
+      return { success: false, error: 'Upload annule' }
+    }
+    return { success: false, error: 'Erreur reseau (Drive)' }
+  }
+}
+
+// ---------------------------------------------------------------------------
+// Upload files to GitHub (with Blender compression)
+// ---------------------------------------------------------------------------
+
+/** Upload files to GitHub (with Blender compression). */
+export async function uploadGit(
+  folder: FolderEntry,
+  secret: string,
+  destination: string,
+  onProgress: (pct: number) => void,
+  signal?: AbortSignal,
+): Promise<{ success: boolean; filename?: string; error?: string }> {
+  const formData = buildUploadFormData(folder, destination)
+
+  onProgress(10)
+
+  try {
+    const res = await fetch('/api/upload/git', {
+      method: 'POST',
+      headers: { 'x-upload-secret': secret.trim() },
+      body: formData,
+      signal,
+    })
+
+    onProgress(80)
+    const data = await res.json()
+
+    if (!data.success) {
+      return { success: false, error: data.error }
+    }
+
+    onProgress(100)
+    return { success: true, filename: folder.folderName }
+  } catch (err) {
+    if (err instanceof DOMException && err.name === 'AbortError') {
+      return { success: false, error: 'Upload annule' }
+    }
+    return { success: false, error: 'Erreur reseau' }
+  }
+}