feat(hotkeys): persistent conflict marker in Settings

A toast is gone by the time the user opens Settings, so a hotkey Windows
refused looked perfectly configured while doing nothing. The offending row now
carries a ⚠ marker (amber border + tooltip explaining the combo is taken)
until a re-registration clears it.

Delphi reports slot ids instead of labels; HOTKEY_SLOTS maps id → button +
label in one place, so JS owns the wording and can flag the exact row. The
markers are re-applied by openSettings, surviving panel re-renders.

Also stop toasting success on the startup push (it fires on every unlock) —
autofillPushHotkeys(true). A clash still warns: that one is actionable.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

css/style.css

@@ -2617,6 +2617,16 @@ body[data-editor-position="center"]:has(#settingsPanel.is-open)::before {
     min-width: 140px;
     text-align: center;
 }
+/* Combo refused by Windows (another app holds it) — the hotkey is dead, so the
+   row has to say so long after the toast is gone. ⚠ via ::after so no markup
+   change is needed when the state flips. */
+.hotkey-capture-btn.is-conflict {
+    border-color: var(--warning, #e0a800);
+    color: var(--warning, #e0a800);
+}
+.hotkey-capture-btn.is-conflict::after {
+    content: " ⚠";
+}
 .hotkey-capture-btn.is-capturing {
     background: var(--accent);
     color: var(--accent-fg, #fff);