feat(accounting): document colleague trades on configured accounts

Post Montzar-covered buy/sell to Zarin/Tahesab/Pargar using montzar_account_* settings, and harden public storage URL/MIME handling for uploads.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/Http/Controllers/Admin/FileController.php

@@ -40,9 +40,7 @@ class FileController extends Controller
 
         $path = $this->createDir();
         $originalName = $uploaded->getClientOriginalName();
-        $ext = $uploaded->getClientOriginalExtension()
-            ?: $uploaded->extension()
-            ?: 'jpg';
+        $ext = $this->resolveUploadExtension($uploaded);
         $title = $request->input('title') ?: $originalName;
         $file_name_src = md5(time().$originalName);
         $file_name = $file_name_src.'.'.$ext;
@@ -70,4 +68,35 @@ class FileController extends Controller
 
         return response()->json($payload);
     }
+
+    /**
+     * پسوند واقعی فایل (MIME)، نه اسم اصلی مرورگر — آپلود بنر WebP است.
+     */
+    private function resolveUploadExtension(\Illuminate\Http\UploadedFile $uploaded): string
+    {
+        $mime = strtolower((string) ($uploaded->getMimeType() ?: $uploaded->getClientMimeType()));
+        $fromMime = match (true) {
+            str_contains($mime, 'webp') => 'webp',
+            str_contains($mime, 'png') => 'png',
+            str_contains($mime, 'jpeg'), str_contains($mime, 'jpg') => 'jpg',
+            str_contains($mime, 'gif') => 'gif',
+            str_contains($mime, 'svg') => 'svg',
+            default => null,
+        };
+        if ($fromMime) {
+            return $fromMime;
+        }
+
+        $client = strtolower((string) $uploaded->getClientOriginalExtension());
+        if (in_array($client, ['webp', 'png', 'jpg', 'jpeg', 'gif', 'svg'], true)) {
+            return $client === 'jpeg' ? 'jpg' : $client;
+        }
+
+        $guessed = strtolower((string) $uploaded->extension());
+        if (in_array($guessed, ['webp', 'png', 'jpg', 'jpeg', 'gif', 'svg'], true)) {
+            return $guessed === 'jpeg' ? 'jpg' : $guessed;
+        }
+
+        return 'jpg';
+    }
 }