test(gateway): fix order-dependent telegram-mock flake cluster

The file-local telegram mock in test_dm_topics.py installed unconditionally
(no __file__ guard), registered a separate string-valued telegram.constants
module, and force-popped the adapter — poisoning the session for any later
telegram test in the same process (assert 'MARKDOWN_V2' in "'MarkdownV2'").

Fix at the source:
- conftest: _FakeEnumMember(str) with PTB-faithful str()==value and
  repr()==<ChatType.X: 'x'>, satisfying both repr assertions and the
  adapter's str(chat.type) normalization; the same object is bound to
  mod.ParseMode and mod.constants.ParseMode.
- test_dm_topics.py: delete the divergent local mock installer; import the
  shared conftest one.
- release.py: mailmap entry for the author.

Verified: the 5-failure cluster repro (dm_topics + slash_confirm +
approval_buttons + model_picker + network_reconnect + telegram_format in one
process) goes 83/83 green (3x); full tests/gateway single-process run drops
10 -> 5 failed, the remainder being pre-existing discord order-dep failures
out of scope here.

Salvaged from #68873. Credit to @liuhao1024 for the earliest root-cause
diagnosis of this str-enum mock class in PR #33875, two months earlier.

Fixes the telegram-mock order-dependent flake cluster.

scripts/release.py

@@ -1025,6 +1025,7 @@ LEGACY_AUTHOR_MAP = {
     "137614867+cutepawss@users.noreply.github.com": "cutepawss",
     "96793918+memosr@users.noreply.github.com": "memosr",
     "mehmet.sr35@gmail.com": "memosr",
+    "mehmet.kar@std.yildiz.edu.tr": "mehmetkr-31",
     "milkoor@users.noreply.github.com": "milkoor",
     "xuerui911@gmail.com": "Fatty911",
     "131039422+SHL0MS@users.noreply.github.com": "SHL0MS",