Drop the .com wordmark from the logo

The logo baked "ihasmail.com" into the artwork, which is the wrong
identity for a project that is not the hosted instance -- and at the
34px the topbar renders it at, the wordmark was an illegible smudge
under a squashed cat.

logo.png, icon-512.png, icon-192.png and apple-touch-icon.png are now
the mark alone. favicon-64.png, icon-maskable.png and favicon.ico
already were, and are untouched.

Cropping needed a threshold: both source files carry a band of
near-invisible pixels (alpha 1-10) roughly 40px wide down the left
side, so a plain getbbox() crop leaves the mark sitting off-centre.
The bounding box is taken at alpha > 8 instead.

The login page had no name of its own -- it relied on the wordmark --
so it gets one as text, styled like the topbar's. Its screenshot is
retaken; the rest still show the old mark in the topbar.

web/src/views/Login.tsx

@@ -52,7 +52,8 @@ export function LoginPage() {
     <div className="login-page">
       <form className="login-card" onSubmit={submit}>
         <div className="logo">
-          <img src="/img/logo.png" alt="" width={120} height={113} />
+          <img src="/img/logo.png" alt="" width={120} height={143} />
+          <h1>ihasmail</h1>
           <p className="tagline">Fast, friendly webmail. Your mailbox, your way.</p>
         </div>
         {error && (