fix: Firefox signing errors — manifest format + JS syntax

1. Removed data_collection_permissions from Firefox manifest — it
   requires Firefox 140+ but we target 128+. Only produces a warning
   when missing, not a blocking error.

2. Fixed JS syntax error in content.js line 450 — two extra closing
   braces from a bad merge in the proper noun detection function
   caused a parse error that blocked Mozilla validation.

https://claude.ai/code/session_01SWSwDfMVij53bCTNSCLMwn

manifest.firefox.json

@@ -6,12 +6,7 @@
   "browser_specific_settings": {
     "gecko": {
       "id": "silent-send@example.com",
-      "strict_min_version": "128.0",
-      "data_collection_permissions": {
-        "required": false,
-        "optional": false,
-        "description": "Silent Send does not collect, transmit, or store any data externally. All processing is 100% local in your browser."
-      }
+      "strict_min_version": "128.0"
     }
   },
   "permissions": [

src/content/content.js

@@ -443,8 +443,6 @@
         });
       }
     }
-      }
-    }
 
     // Deduplicate
     const seen = new Set();