fix(account): one form and one Save for your account; the same for an account's page in Users

Operator review of the Account page: two sections with two different
save buttons, one stuck to the next card and one beside a squeezed hint.
- Account: time zone and Email are one form; POST /account/ saves both,
  nothing unless all of it is valid. /account/email is gone.
- Users › account: Name and Email are one form; the rename route also
  saves the email switches. /settings/users/<id>/email is gone.
- The Email section is a plain section now (email_section); its hint sits
  under the switches, names the zone as the picker does, and links
  Notifications only for an admin.
- apply_email_form leaves a switch the form doesn't carry as it is.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/integration/test_account_time_zone.py

@@ -73,7 +73,7 @@ def test_the_browser_zone_is_adopted_once_and_the_account_page_changes_it(app):
     assert out["adopt"] == {"adopted": True} and out["after_adopt"] == "America/New_York"
     assert out["again"] == {"adopted": False}
     page = out["page"]
-    assert "times show in <strong>America/New_York</strong> (E" in page        # EDT or EST
+    assert "times show in <strong>New York</strong> (E" in page               # EDT or EST
     assert '<option value="America/New_York" selected>New York</option>' in page
     assert "/account/time-zone/adopt" not in page                              # nothing left to adopt
     assert out["save"] == (302, "/account/") and out["after_save"] == "Europe/London"