Modern in the logo's colours, and the logo in the page's mode (#63)

Modern's palette was sampled from the 2004 iPodderX icon: a neutral navy,
its screen blue and amber EQ bars. It now takes the new logo's colours,
the dark half from logo-dark.svg (navy ground, #8fc2ea scale, #ff6a1a
needle) and the light half from logo.svg (sky ground, #2f6aa0 scale, the
needle taken down to #c43e00 so white on it clears AA). The pending amber
and the error red moved apart from the needle's orange, and the sign-in
page's copy of the palette follows.

The pages always showed logo.svg, the light variant, even in a dark
theme; logo-dark.svg was never served. It is now, and the app and admin
pages show whichever matches data-mode, dark until the script says light,
as the palette is. The sign-in page, which has no account's theme, picks
by the system's with <picture>.

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

web/index.html

@@ -14,7 +14,7 @@
   <button class="iconbtn" id="burger" title="Feeds" aria-label="Feeds" data-icon="menu"></button>
   <!-- One group per thing acted on, in the order the panes read: feeds, then the selected item.
        A phone hides the item group, which it has no table for. -->
-  <img class="logo" id="applogo" src="/logo.svg" alt="iPX" title="iPX {version}">
+  <span id="applogo" title="iPX {version}"><img class="logo onlight" src="/logo.svg" alt="iPX"><img class="logo ondark" src="/logo-dark.svg" alt="iPX"></span>
   <div class="tgroup">
     <button id="addFeed" title="Add a feed" aria-label="Add a feed" data-icon="plus"></button>
     <button id="tbRemove" title="Unsubscribe from this feed" aria-label="Unsubscribe from this feed" data-icon="circleMinus" disabled></button>