Add Tuta logo to the GUI header

Use the Tuta brand mark (from the tutanota repo) as a small icon next
to the TutaBridge title. Trademark belongs to Tuta — used here only to
identify the service the bridge connects to.

ui/src/App.css

@@ -23,6 +23,12 @@
   gap: 14px;
 }
 
+.app-logo {
+  display: block;
+  border-radius: 6px;
+  flex-shrink: 0;
+}
+
 .app-header h1 {
   font-family: var(--brand);
   font-size: 16px;

ui/src/App.tsx

@@ -6,6 +6,7 @@ import { ConfigPanel } from "./components/ConfigPanel";
 import { LogsPanel } from "./components/LogsPanel";
 import { BackupPanel } from "./components/BackupPanel";
 import { statusLabel, isError } from "./types";
+import logo from "./assets/tuta-logo.svg";
 import "./App.css";
 
 type Tab = "dashboard" | "connection" | "config" | "backup" | "logs";
@@ -29,6 +30,7 @@ function App() {
     <div className="app">
       <header className="app-header">
         <div className="header-left">
+          <img src={logo} alt="" className="app-logo" width={24} height={24} />
           <h1>TutaBridge</h1>
           <div className="header-status">
             <span className="status-dot" style={{ background: statusColor }} />

ui/src/assets/tuta-logo.svg

@@ -0,0 +1,6 @@
+<svg width="62" height="62" viewBox="0 0 62 62" fill="none" xmlns="http://www.w3.org/2000/svg">
+<rect width="62" height="62" rx="12" fill="#850122"/>
+<path d="M15.9578 12.6791L22.3603 19.1475C22.51 19.297 22.6598 19.3344 22.8844 19.3344H49.8796C50.0668 19.3344 50.1792 19.1101 49.9919 18.9231L43.6644 12.5296C43.5146 12.38 43.3649 12.3052 43.0653 12.3052H16.1076C15.8455 12.3052 15.8081 12.5296 15.9578 12.6791Z" fill="white"/>
+<path d="M15.0218 49.3957C14.9844 49.5452 15.0592 49.6948 15.2465 49.6948H41.8673C42.1293 49.6948 42.2416 49.5826 42.3165 49.3583L50.3664 23.41C50.4412 23.1483 50.329 23.0735 50.1043 23.0735H23.4087C23.1841 23.0735 23.1092 23.1483 23.0343 23.3352L15.0218 49.3957Z" fill="white"/>
+<path d="M13 41.9177C13 42.2168 13.3744 42.2168 13.4493 41.9177L19.5522 22.0639C19.6271 21.8395 19.6271 21.69 19.4399 21.503L13.3744 15.4833C13.2246 15.3337 13 15.4085 13 15.5955V41.9177Z" fill="white"/>
+</svg>