[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.

public/brand-assets/logo_thumbnail.svg

@@ -1,25 +0,0 @@
-<svg
-  width="16"
-  height="16"
-  viewBox="0 0 16 16"
-  fill="none"
-  xmlns="http://www.w3.org/2000/svg"
->
-  <g clip-path="url(#woot-logo-clip-2342424e23u32098)">
-    <path
-      d="M8 16C12.4183 16 16 12.4183 16 8C16 3.58172 12.4183 0 8 0C3.58172 0 0 3.58172 0 8C0 12.4183 3.58172 16 8 16Z"
-      fill="#2781F6"
-    />
-    <path
-      d="M11.4172 11.4172H7.70831C5.66383 11.4172 4 9.75328 4 7.70828C4 5.66394 5.66383 4 7.70835 4C9.75339 4 11.4172 5.66394 11.4172 7.70828V11.4172Z"
-      fill="white"
-      stroke="white"
-      stroke-width="0.1875"
-    />
-  </g>
-  <defs>
-    <clipPath id="woot-logo-clip-2342424e23u32098">
-      <rect width="16" height="16" fill="white" />
-    </clipPath>
-  </defs>
-</svg>

public/manifest.json

@@ -1,6 +1,6 @@
 {
-  "name": "Chatwoot",
-  "short_name": "Chatwoot",
+  "name": "Moreminimore Chat",
+  "short_name": "Moreminimore Chat",
   "icons": [{
     "src": "\/android-icon-36x36.png",
     "sizes": "36x36",