fix(mobile): iOS share sheet, empty files tab, and stuck upload status

- app.json: add CFBundleDocumentTypes to iOS infoPlist so the app
  appears in the iOS Share Sheet; add ACTION_SEND/SEND_MULTIPLE
  intentFilters for Android share intent support

- src/context/ShareContext.tsx (new): React context that queues files
  received from the share sheet and delivers them to UploadScreen

- app/_layout.tsx: wrap in ShareProvider; add Linking handler
  (makeUrlHandler factory + getInitialURL cold-start + addEventListener
  warm-start) to capture file:// and content:// URLs

- src/services/api.ts: fix FileRecord interface (original_filename,
  nested ProcessingStatus, mime_type); fix UploadResponse interface;
  fix listFiles() (per_page param, unwrap data.files); add
  getFileStatus(fileId) for single-file status polling

- src/screens/FilesScreen.tsx: use file.original_filename and
  file.processing_status.status; fix statusEmoji to use actual backend
  status values (completed/pending/duplicate)

- src/screens/UploadScreen.tsx: consume ShareContext for auto-upload of
  shared files; add 5-second polling loop (search by filename → file_id
  → getFileStatus) to show real-time server processing status;
  uploadFile wrapped in useCallback; proper effect dependency arrays

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

mobile/src/context/ShareContext.tsx

@@ -0,0 +1,51 @@
+/**
+ * ShareContext – propagates files received from the iOS Share Sheet or the
+ * Android Share Intent to the UploadScreen so they can be uploaded
+ * automatically.
+ *
+ * The root layout listens for incoming file:// / content:// URLs via
+ * expo-linking and calls addPendingFile().  UploadScreen consumes the context,
+ * uploads each pending file, then calls clearPendingFiles().
+ */
+
+import React, { createContext, useCallback, useContext, useState } from "react";
+
+export interface SharedFile {
+  uri: string;
+  filename: string;
+  mimeType?: string;
+}
+
+interface ShareContextValue {
+  pendingFiles: SharedFile[];
+  addPendingFile: (file: SharedFile) => void;
+  clearPendingFiles: () => void;
+}
+
+const ShareContext = createContext<ShareContextValue>({
+  pendingFiles: [],
+  addPendingFile: () => {},
+  clearPendingFiles: () => {},
+});
+
+export function ShareProvider({ children }: { children: React.ReactNode }) {
+  const [pendingFiles, setPendingFiles] = useState<SharedFile[]>([]);
+
+  const addPendingFile = useCallback((file: SharedFile) => {
+    setPendingFiles((prev) => [...prev, file]);
+  }, []);
+
+  const clearPendingFiles = useCallback(() => {
+    setPendingFiles([]);
+  }, []);
+
+  return (
+    <ShareContext.Provider value={{ pendingFiles, addPendingFile, clearPendingFiles }}>
+      {children}
+    </ShareContext.Provider>
+  );
+}
+
+export function useShare(): ShareContextValue {
+  return useContext(ShareContext);
+}