Mail: account cards, choose which mail apps to show, optional framed webmail

- Mail page redesigned as one card per account (inbox + compose)
- Settings -> Mail apps: tick the apps you use; saved on the server per person
- WEBMAIL_URL shows your own webmail (e.g. Roundcube) inside the Mail tab; provider shortcuts one tap away
- README: Roundcube setup and framing headers

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

public/style.css

@@ -301,3 +301,20 @@ input, textarea, [contenteditable], .sheet p, .card p, #view .sub { -webkit-user
 #navbar #nvt { color: var(--muted); font-size: 13px; margin-left: 6px; }
 body:not(.editing) #view { padding-top: 8px; }
 @media (min-width: 768px) { #navbar { padding-left: 24px; } body:not(.editing) #view { padding-top: 12px; } }
+
+/* Mail */
+.mailgrid { display: grid; gap: 14px; grid-template-columns: 1fr; margin-top: 16px; }
+@media (min-width: 768px) { .mailgrid { grid-template-columns: repeat(2, 1fr); } }
+.mcard { background: var(--panel); border: 1px solid var(--line); border-radius: 18px; padding: 16px; position: relative; overflow: hidden; display: flex; flex-direction: column; gap: 16px; }
+.mcard::before { content: ''; position: absolute; left: 0; top: 0; right: 0; height: 4px; background: var(--mc); }
+.mhd { display: flex; align-items: center; gap: 12px; }
+.mhd .grow { flex: 1; min-width: 0; }
+.mhd b, .mhd small { display: block; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
+.mhd b { font-size: 17px; }
+.mhd small { color: var(--muted); }
+.mbadge { width: 48px; height: 48px; border-radius: 14px; background: var(--mc); color: #fff; display: grid; place-items: center; flex: none; }
+.mbadge svg { width: 26px; height: 26px; }
+.mact { display: flex; gap: 8px; }
+.mact .btn { flex: 1; display: inline-flex; align-items: center; justify-content: center; gap: 8px; min-height: 46px; }
+.mact .btn svg { width: 20px; height: 20px; }
+.mact .btn:not(.ghost) { background: var(--mc); color: #fff; }