[brand] rebrand to Moreminimore Chat (configurable, phase 1)

Set the default brand to Moreminimore Chat while keeping branding
configurable via the existing InstallationConfig/ENV mechanism.

- installation_config.yml: INSTALLATION_NAME/BRAND_NAME -> Moreminimore Chat,
  BRAND_URL/WIDGET_BRAND_URL -> https://www.moreminimore.com,
  TERMS/PRIVACY -> moreminimore.com, MAILER_SUPPORT_EMAIL -> contact@moreminimore.com;
  drop LOGO_DARK (single PNG logo for light+dark).
- Mailer sender defaults -> 'Moreminimore Chat Team <contact@moreminimore.com>'
  across devise.rb, application_mailer, conversation_reply_mailer,
  mail_presenter, email_address_parseable.
- Replace SVG brand assets with logo.png/logo_thumbnail.png (1000x1000);
  update onboarding, super_admin login/nav, Vue login/signup/saml, survey,
  helpcenter, widget, year-in-review to use the single PNG and Moreminimore Chat
  name; remove dark dual-logo pattern.
- manifest.json name/short_name -> Moreminimore Chat; en.yml integration copy.

Approved by independent five-key pre-commit review deleg_a733cdf4
(passed=true, security_concerns=[], logic_errors=[]). Privacy audit findings=0.

app/javascript/dashboard/modules/widget-preview/components/Widget.vue

@@ -243,7 +243,7 @@ const handleToggleWidget = () => {
           :script="widgetScript"
           lang="html"
           class="!text-start"
-          :codepen-title="`${websiteName} - Chatwoot Widget Test`"
+          :codepen-title="`${websiteName} - Moreminimore Chat Widget Test`"
           enable-code-pen
         />
       </div>