feat(market): line/candle toggle + ~50% taller chart

- Add a chart-style toggle (line vs candlestick) next to the interval buttons,
  shown only when the selected range has per-exchange candles (the aggregate /
  Live view is line-only). It flips s_mkt.chartStyle; candles draw when OHLC
  exists AND the user hasn't switched to the line. Icon reflects the current
  style; tooltip says what a click switches to. Two i18n keys across 8 languages.
- Make the price chart ~50% taller: scale the height floor / desired / viewport
  cap (110->165, x1.5 desired, 0.22->0.33 of available) for a roomier plot.

Verified via a forced-OHLC render: the taller chart, the toggle button, and
candles with a correct week/day x-axis.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/util/i18n.cpp

@@ -1348,6 +1348,8 @@ void I18n::loadBuiltinEnglish()
         strings_["market_btc_price"] = "BTC PRICE";
         strings_["market_no_history"] = "No price history available";
         strings_["market_chart_loading"] = "Loading price history";
+        strings_["market_style_line"] = "Switch to line chart";
+        strings_["market_style_candle"] = "Switch to candlesticks";
         strings_["market_no_price"] = "No price data";
         strings_["market_now"] = "Now";
         strings_["market_pct_shielded"] = "%.0f%% Shielded";