feat: collapsible Flex/amp/tuner cards, matched meter sizes, faster + distinct-icon TGXL

Addresses three points of feedback on the Tuner Genius work:

- Meter sizes: the amplifier meters were rendered `compact` (smaller than the
  FlexRadio meters). Dropped compact so the amp, tuner and Flex meters are all
  the same size.
- Collapsible cards: the FlexRadio panel Card, AmpCard and TunerCard now fold
  from a chevron in the header, state persisted per card (opslog.cardOpen.*).
  The amplifier cards share the "amplifier" collapse key across their SPE/ACOM/
  PGXL variants so folding sticks regardless of the shown model.
- TGXL responsiveness: the tuner's device poll dropped 1500ms→400ms and the
  three UI pollers 1500ms→500ms, so the SWR/power meters track TX without the
  2–3s lag behind the amplifier the user saw.
- Icon: the Tuner Genius top-bar toggle used Zap, same as the CW keyer — changed
  the tuner's icon (top bar + widget + card) to Gauge so the two are distinct.

frontend/src/components/StationControlPanel.tsx

@@ -298,7 +298,7 @@ export function StationControlPanel({ centerLat, centerLon, bearing }: RotatorPr
       try { const s: any = await GetTunerGeniusStatus(); if (alive && s) setTg(s as TGStatus); } catch {}
     };
     load();
-    const id = window.setInterval(load, 1500);
+    const id = window.setInterval(load, 500); // fast so meters track TX (see App.tsx)
     return () => { alive = false; window.clearInterval(id); };
   }, []);