Prevent csv export injections (#14347)

**Small Security Issue:** CSV exports were vulnerable to formula
injection attacks when users entered values starting with =, +, -, or @.
(only happens if a logged-in user injects corrupted data)

Solution:
- Added ZWJ (Zero-Width Joiner) protection that prefixes dangerous
values with invisible Unicode character
- This is the best way to preserve original data while preventing Excel
from executing formulas
- Added import cleanup to restore original values when re-importing
 
Changes:
- New sanitizeValueForCSVExport() function for security
- Updated all CSV export paths to use both security + formatting
functions
- Added comprehensive tests covering attack vectors and international
characters
- Also added cursor rules for better code consistency

---------

Co-authored-by: Charles Bochet <charlesBochet@users.noreply.github.com>

packages/twenty-front/src/modules/spreadsheet-import/utils/mapWorkbook.ts

@@ -1,3 +1,4 @@
+import { cleanZWJFromImportedValue } from '@/spreadsheet-import/utils/cleanZWJFromImportedValue';
 import { utils, type WorkBook } from 'xlsx-ugnis';
 
 export const mapWorkbook = (workbook: WorkBook, sheetName?: string) => {
@@ -7,5 +8,14 @@ export const mapWorkbook = (workbook: WorkBook, sheetName?: string) => {
     blankrows: false,
     raw: false,
   });
-  return data as string[][];
+
+  // Clean ZWJ characters from imported CSV data to restore original values
+  // This reverses the ZWJ protection applied during export
+  const cleanedData = (data as string[][]).map((row) =>
+    row.map((cell) =>
+      typeof cell === 'string' ? cleanZWJFromImportedValue(cell) : cell,
+    ),
+  );
+
+  return cleanedData;
 };