fix(mobile): add shared file to ShareContext directly in +not-found.tsx

When iOS delivers a file via "Open In…", expo-router strips the
docuelevate:// scheme and routes to +not-found.tsx. Previously, this
screen only redirected to the Upload tab and relied on the Linking
handler in _layout.tsx to add the file to ShareContext. This was
unreliable because expo-router may consume the URL event before the
Linking handler fires.

Now +not-found.tsx directly reconstructs the file:// URI from the
pathname and adds it to ShareContext before redirecting. ShareContext
deduplicates by URI to prevent double uploads if both mechanisms fire.

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

mobile/app/+not-found.tsx

@@ -10,10 +10,13 @@
  *    no such route exists, expo-router previously threw "unmatched route
  *    docuelevate://…" and the upload never happened.
  *
- *    This screen detects the filesystem-path pattern and immediately redirects
- *    to the Upload tab.  The `Linking` listener registered in `_layout.tsx`
- *    runs concurrently and adds the file to `ShareContext`; `UploadScreen`
- *    picks it up and begins uploading as soon as the redirect completes.
+ *    This screen detects the filesystem-path pattern, adds the file directly
+ *    to `ShareContext`, and redirects to the Upload tab.  `UploadScreen`
+ *    picks up the pending file and begins uploading automatically.
+ *
+ *    The `Linking` listener in `_layout.tsx` may also fire for the same URL;
+ *    `ShareContext.addPendingFile` deduplicates by URI so the file is only
+ *    uploaded once.
  *
  * 2. **Any other unmatched in-app route** — redirect silently to the root so
  *    the user isn't left on a blank error page.
@@ -22,6 +25,7 @@
 import { usePathname, useRouter } from "expo-router";
 import React, { useEffect } from "react";
 import { ActivityIndicator, StyleSheet, View } from "react-native";
+import { useShare } from "../src/context/ShareContext";
 
 // ---------------------------------------------------------------------------
 // Helpers
@@ -81,6 +85,21 @@ function looksLikeFilePath(pathname: string): boolean {
   return !IN_APP_ROUTE_PREFIXES.some((prefix) => stripped.startsWith(prefix));
 }
 
+/**
+ * Extract a display filename from a filesystem path.
+ * Handles URL-encoded characters and strips query strings.
+ */
+function filenameFromPath(pathname: string): string {
+  try {
+    const decoded = decodeURIComponent(pathname);
+    const segments = decoded.split("/").filter(Boolean);
+    const last = segments[segments.length - 1] ?? "shared_file";
+    return last.split("?")[0] || "shared_file";
+  } catch {
+    return "shared_file";
+  }
+}
+
 // ---------------------------------------------------------------------------
 // Screen component
 // ---------------------------------------------------------------------------
@@ -88,18 +107,26 @@ function looksLikeFilePath(pathname: string): boolean {
 export default function NotFoundScreen() {
   const pathname = usePathname();
   const router = useRouter();
+  const { addPendingFile } = useShare();
 
   useEffect(() => {
     if (looksLikeFilePath(pathname)) {
-      // Filesystem path from iOS "Open In…" – redirect to Upload tab.
-      // The Linking listener in _layout.tsx has already (or will shortly)
-      // added the file to ShareContext; UploadScreen will pick it up.
+      // Filesystem path from iOS "Open In…" – add the file to ShareContext
+      // and redirect to the Upload tab.  UploadScreen will pick up the
+      // pending file and begin uploading automatically.
+      //
+      // The pathname from expo-router is the raw filesystem path
+      // (e.g. "/private/var/mobile/Library/…/file.pdf").  Reconstruct a
+      // file:// URI so the upload logic can read the file.
+      const fileUri = `file://${pathname}`;
+      const filename = filenameFromPath(pathname);
+      addPendingFile({ uri: fileUri, filename });
       router.replace("/(tabs)/");
     } else {
       // Truly unknown in-app route – fall back to the root redirect.
       router.replace("/");
     }
-  }, [pathname, router]);
+  }, [pathname, router, addPendingFile]);
 
   // Show a brief spinner while the redirect is in flight.
   return (