Rebrand to INBUXA: product name, protocol greetings, sign-in page, calendar templates, logos, README

One branding module (types::brand!) supplies the name to every protocol
greeting, the HTTP realm, the startup banner, Received headers, the
user agent, the IMAP ID response and calendar PRODIDs. The sign-in and
calendar pages take ihasmail's palette and font and the INBUXA logo, and
calendar emails embed the INBUXA lockup. Default calendar and address book
names follow. Protocol identifiers (urn:stalwart:jmap, vnd.stalwart Sieve
extensions) and upstream copyright notices are unchanged.

resources/html-templates/calendar-alarm.html

@@ -50,7 +50,7 @@
         }
 
         a {
-            color: #185fa5;
+            color: #0f766e;
         }
 
         @media only screen and (max-width:600px) {
@@ -143,7 +143,7 @@
                                                         {{key}}</div>
                                                     <div
                                                         style="font-family:-apple-system,'Segoe UI',Roboto,Helvetica,Arial,sans-serif;font-size:15px;line-height:1.5;color:#1a1a18;padding-top:3px;word-break:break-word;">
-                                                        {{#if link}}<a href="{{link}}" target="_blank" style="color:#185fa5;text-decoration:underline;">{{/if link}}{{value}}{{#if link}}</a>{{/if link}}</div>
+                                                        {{#if link}}<a href="{{link}}" target="_blank" style="color:#0f766e;text-decoration:underline;">{{/if link}}{{value}}{{#if link}}</a>{{/if link}}</div>
                                                 </td>
                                             </tr>
                                             {{/each event_details}}

resources/html-templates/calendar-invite.html

@@ -50,7 +50,7 @@
         }
 
         a {
-            color: #185fa5;
+            color: #0f766e;
         }
 
         .bar-info {
@@ -192,7 +192,7 @@
                                                         {{old_value}}</div>{{/if old_value}}
                                                     <div
                                                         style="font-family:-apple-system,'Segoe UI',Roboto,Helvetica,Arial,sans-serif;font-size:15px;line-height:1.5;color:#1a1a18;padding-top:3px;word-break:break-word;">
-                                                        {{#if link}}<a href="{{link}}" target="_blank" style="color:#185fa5;text-decoration:underline;">{{/if link}}{{value}}{{#if link}}</a>{{/if link}}</div>
+                                                        {{#if link}}<a href="{{link}}" target="_blank" style="color:#0f766e;text-decoration:underline;">{{/if link}}{{value}}{{#if link}}</a>{{/if link}}</div>
                                                 </td>
                                             </tr>
                                             {{/each event_details}}