Toolbar: konsistent formspråk − + × ○ #

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/lib/components/canvas/Canvas.svelte

@@ -531,7 +531,7 @@
 			onclick={() => zoomToFit()}
 			title="Tilpass visning"
 			aria-label="Tilpass visning"
-		>⊡</button>
+		>○</button>
 		<div class="canvas-toolbar-sep"></div>
 		<button
 			class="canvas-toolbar-btn"
@@ -545,7 +545,7 @@
 			onclick={toggleFullscreen}
 			title="Fullskjerm"
 			aria-label="Fullskjerm"
-		>{isFullscreen ? '⊖' : '⊕'}</button>
+		>{isFullscreen ? '−' : '+'}</button>
 	</div>
 
 	<!-- Grid background (when enabled) -->