Logbook: re-tapping the Logbook tab should scroll the list to top

## What
Re-tapping the **Logbook** tab button while already on the Logbook page should scroll the flight list back to top (smooth) if it's scrolled down. Standard iOS tab convention, and it complements the status-bar-tap fix.

Today the Logbook `IonTabButton` (`src/ui/App.tsx:149-152`) has no re-tap handling, and nothing scrolls the virtualized list to top.

## Depends on #96
This shares the exact primitive built there: "scroll the active Logbook `virtua` list to top." Voyager keeps these two paths deliberately parallel — a `statusTap` listener and a separate `scrollUpIfNeeded` for tab re-tap — and even flags them as semi-duplicated:
- `src/helpers/scrollUpIfNeeded.ts` — https://github.com/aeharding/voyager/blob/main/src/helpers/scrollUpIfNeeded.ts (reads the virtua handle's `scrollOffset` to decide whether a scroll is needed, then scrolls the `.virtual-scroller` node / calls `scrollToIndex(0, { smooth })`).

So: land #96 first, extract the shared helper, then this issue just wires it to the tab re-tap.

## Implementation notes
- **Detect the re-tap.** Ionic React's `onIonTabsWillChange` does not fire when the active tab is tapped again, so this needs handling on the Logbook `IonTabButton` itself (intercept its click / router event when the current route is already `/logbook`). Worth checking how Voyager's tab bar detects re-selection.
- **Scroll only if needed.** Read the `virtua` `VirtualizerHandle.scrollOffset` (exposed via the `FlightList` `virtualizer` ref, `src/ui/logbook/FlightList.tsx`) — if `> 0`, call the shared scroll-to-top helper (`scrollTo(0)` / `scrollToIndex(0, { smooth: true })`, or scroll the `IonContent` inner element).
- Unlike the status-bar tap (second-tap-restores-position), a tab re-tap should just go to top; no need to restore.

## Acceptance criteria
- On the Logbook page, scroll down, tap the Logbook tab again → list smooth-scrolls to top.
- Tapping the Logbook tab from another tab still just navigates (no unexpected scroll jump).
- When already at top, a re-tap is a no-op (no jitter).

## References
- Wingover: `src/ui/App.tsx:149-152` (Logbook `IonTabButton`), `src/ui/logbook/FlightList.tsx` (`virtualizer` handle)
- Voyager `scrollUpIfNeeded.ts`: https://github.com/aeharding/voyager/blob/main/src/helpers/scrollUpIfNeeded.ts
- Voyager `useGetAppScrollable.ts`: https://github.com/aeharding/voyager/blob/main/src/helpers/useGetAppScrollable.ts
- virtua `VirtualizerHandle` (`scrollOffset`, `scrollTo`, `scrollToIndex`): https://github.com/inokawa/virtua/blob/main/src/react/Virtualizer.tsx