Fix malformed race clock format and refresh docs screenshots

formatRaceClock rendered a doubled-up, garbled time (e.g.
"02:48.20:207") everywhere a race clock is shown - Timing, Overlay,
Results archive, Judging, Training stint logs - because it
concatenated both a centiseconds and a milliseconds computation into
the same string. Only the milliseconds part was ever meant to be
there. Found while building realistic demo data for new screenshots,
since every prior test/demo session was empty and never exercised
this code path with a real result.

Also regenerates all screenshots in docs/screenshots against a
realistic seeded race (drivers, cars, qualifying heats, finals,
practice history, a real judging correction) instead of empty demo
data, adds two new ones (Managed AMMC config, the in-app Guide page)
aimed at helping a new user understand initial setup, removes 6
screenshots orphaned by an earlier README revision, and updates both
README.md and README.sv.md's screenshot tables accordingly.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

README.md

@@ -76,6 +76,10 @@ Current layouts for race operation, live presentation, training and system confi
   </tr>
   <tr>
     <td width="50%"><a href="docs/screenshots/decoder-settings.jpg"><img src="docs/screenshots/decoder-settings.jpg" alt="Decoder configuration" /></a><br><strong>Decoder configuration</strong></td>
+    <td width="50%"><a href="docs/screenshots/managed-ammc.jpg"><img src="docs/screenshots/managed-ammc.jpg" alt="Managed AMMC configuration" /></a><br><strong>Managed AMMC configuration</strong></td>
+  </tr>
+  <tr>
+    <td width="50%"><a href="docs/screenshots/guide.jpg"><img src="docs/screenshots/guide.jpg" alt="In-app setup guide" /></a><br><strong>In-app setup guide</strong></td>
     <td width="50%"></td>
   </tr>
 </table>