refactor(mobile): extract shared MIME type utility and improve error handling

- Extract EXT_TO_MIME map and mimeTypeFromFilename to shared module
  at mobile/src/utils/mimeTypes.ts (used by _layout.tsx and +not-found.tsx)
- Add error logging to ensureLocalUri catch block for debugging
- Add error handling to Linking.openURL calls in ProfileScreen
- Fix incorrect LSSupportsOpeningDocumentsInPlace docs in audit report

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

mobile/src/screens/ProfileScreen.tsx

@@ -45,7 +45,9 @@ export default function ProfileScreen() {
           text: "Delete Account",
           style: "destructive",
           onPress: () => {
-            Linking.openURL(`${effectiveBaseUrl}/account/delete`);
+            Linking.openURL(`${effectiveBaseUrl}/account/delete`).catch(() => {
+              Alert.alert("Error", "Could not open the account deletion page. Please try again.");
+            });
           },
         },
       ]
@@ -53,11 +55,15 @@ export default function ProfileScreen() {
   }
 
   function openPrivacyPolicy() {
-    Linking.openURL(`${effectiveBaseUrl}/privacy`);
+    Linking.openURL(`${effectiveBaseUrl}/privacy`).catch(() => {
+      Alert.alert("Error", "Could not open the privacy policy. Please try again.");
+    });
   }
 
   function openTermsOfService() {
-    Linking.openURL(`${effectiveBaseUrl}/terms`);
+    Linking.openURL(`${effectiveBaseUrl}/terms`).catch(() => {
+      Alert.alert("Error", "Could not open the terms of service. Please try again.");
+    });
   }
 
   if (!user) {

mobile/src/screens/UploadScreen.tsx

@@ -95,8 +95,9 @@ export default function UploadScreen() {
     try {
       await FileSystem.copyAsync({ from: uri, to: destUri });
       return destUri;
-    } catch {
+    } catch (copyErr) {
       // Copy failed – fall back to the original URI (might work for some paths).
+      console.warn("[ensureLocalUri] copyAsync failed:", { from: uri, to: destUri, error: copyErr });
       return uri;
     }
   }, []);

mobile/src/utils/mimeTypes.ts

@@ -0,0 +1,44 @@
+/**
+ * Shared MIME type utilities for the DocuElevate mobile app.
+ *
+ * Used by the Linking handler in _layout.tsx, the catch-all +not-found.tsx,
+ * and any other code that needs to infer a MIME type from a file extension.
+ */
+
+/**
+ * Common MIME type mappings for file extensions.
+ * Used to infer the MIME type of files shared via the Share Sheet / "Open In…"
+ * so the server receives a correct Content-Type instead of application/octet-stream.
+ */
+export const EXT_TO_MIME: Record<string, string> = {
+  pdf: "application/pdf",
+  jpg: "image/jpeg",
+  jpeg: "image/jpeg",
+  png: "image/png",
+  gif: "image/gif",
+  bmp: "image/bmp",
+  tiff: "image/tiff",
+  tif: "image/tiff",
+  webp: "image/webp",
+  heic: "image/heic",
+  heif: "image/heif",
+  txt: "text/plain",
+  csv: "text/csv",
+  doc: "application/msword",
+  docx: "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
+  xls: "application/vnd.ms-excel",
+  xlsx: "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
+  ppt: "application/vnd.ms-powerpoint",
+  pptx: "application/vnd.openxmlformats-officedocument.presentationml.presentation",
+  rtf: "application/rtf",
+  html: "text/html",
+  xml: "application/xml",
+  json: "application/json",
+  zip: "application/zip",
+};
+
+/** Infer MIME type from a filename's extension, or undefined if unknown. */
+export function mimeTypeFromFilename(filename: string): string | undefined {
+  const ext = filename.split(".").pop()?.toLowerCase();
+  return ext ? EXT_TO_MIME[ext] : undefined;
+}