fix+feat: fix invisible result values, inline symbol into label

Fix: .result-value was using color: var(--pico-color) which broke when
our custom palette variables weren't in scope. Now inherits body color —
Pico handles light/dark correctly without us needing to re-assert it.

Feat: unit symbol merged inline into label as 'Blurbs (bl)', replacing
the separate third line. Removes .result-symbol CSS rule. Cards are
shorter and less cluttered.

src/components/ConversionResult.svelte

@@ -57,6 +57,5 @@
   aria-pressed={highlighted}
 >
   <span class="result-value">{formattedValue}</span>
-  <span class="result-label">{unit.labelPlural}</span>
-  <span class="result-symbol">{unit.symbol}</span>
+  <span class="result-label">{unit.labelPlural} ({unit.symbol})</span>
 </div>