iOS: Add poll support, fix contact name resolution, fix typos

- Add poll message decoding for iOS (ZMESSAGETYPE 46) using raw protobuf
  parsing of ZWAMESSAGEINFO.ZRECEIPTINFO blobs (no external dependency).
  Polls render with vote tallies and voter names in the HTML export.
- Fix iOS contact name resolution: pull ZFULLNAME from address book,
  resolve LID-based group members, fall back to ZWAPROFILEPUSHNAME,
  and avoid overwriting real names with phone numbers.
- Fix typo: 'expoter' -> 'exporter' in android_crypt.py and __main__.py.
- Add poll field to Message data model and update test fixtures.

tests/test_incremental_merge.py

@@ -107,7 +107,8 @@ chat_data_merged = {
                 "sticker": False,
                 "message_type": None,
                 "received_timestamp": None,
-                "read_timestamp": None
+                "read_timestamp": None,
+                "poll": None
             },
             "24691": {
                 "from_me": False,
@@ -128,7 +129,8 @@ chat_data_merged = {
                 "sticker": False,
                 "message_type": None,
                 "received_timestamp": None,
-                "read_timestamp": None
+                "read_timestamp": None,
+                "poll": None
             },
             "24692": {
                 "from_me": False,
@@ -149,7 +151,8 @@ chat_data_merged = {
                 "sticker": False,
                 "message_type": None,
                 "received_timestamp": None,
-                "read_timestamp": None
+                "read_timestamp": None,
+                "poll": None
             },
         }
     }