fix: theme reverts to light after an update when the logbook DB is slow

An update can clear the WebView's localStorage; the theme is then restored from
the portable DB pref, but GetUIPref returned ("", nil) while the settings store
was still starting (indistinguishable from a genuinely-unset pref), so the
self-heal gave up after ~2.4s and fell back to the light default.

GetUIPref now returns an error when the settings store isn't wired yet, and the
theme self-heal treats that as "not ready → keep retrying" (up to ~36s) vs a
real empty answer ("unset → keep default"). A dark theme survives the relaunch.

frontend/src/lib/theme.tsx

@@ -73,16 +73,23 @@ export function ThemeProvider({ children }: { children: ReactNode }) {
     const load = () => {
       tries += 1;
       GetUIPref(LS_KEY).then((raw) => {
+        // Backend ANSWERED (settings store ready). Apply a valid stored value; an
+        // empty/invalid one means the theme is genuinely unset → keep the default.
+        // Either way we're done — do NOT retry (retrying only matters while the
+        // backend is still starting, which now surfaces as a rejected promise).
         if (cancelled || userPicked.current) return;
         const v = raw as ThemeChoice;
         if (v && ALL.includes(v)) {
           try { localStorage.setItem(LS_KEY, v); } catch { /* quota */ }
           applyThemeToDom(v); // idempotent — safe to call unconditionally
           setThemeState(v);
-          return; // restored
         }
-        if (tries < 8) window.setTimeout(load, 300); // empty (unset or backend not ready yet) → retry
-      }).catch(() => { if (!cancelled && tries < 8) window.setTimeout(load, 300); });
+      }).catch(() => {
+        // Settings store not ready yet — on a slow / remote logbook this can take
+        // many seconds. Keep retrying well past the old 2.4s cap so a dark theme
+        // isn't lost to the light default after an update cleared localStorage.
+        if (!cancelled && !userPicked.current && tries < 120) window.setTimeout(load, 300);
+      });
     };
     load();
     return () => { cancelled = true; };