css: tokenize borders, spacing, and radii — spacing audit pass 4

Phase 1: border widths (1/2/3px → --border-thin/medium/thick) — 76 replacements
Phase 2: adopt existing spacing tokens (--space-xs through --space-xl) — 18 replacements
Phase 3: border-radius scale (--radius-sm/md/lg/pill) — 16 replacements
Total: 110 replacements + 7 new tokens across 7 files

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

SVS-MSP-Calculator-tokens.css

@@ -64,8 +64,15 @@
     --space-2xl: 24px;
     --space-3xl: 28px;
     --space-4xl: 32px;
+    --border-thin: 1px;
+    --border-medium: 2px;
+    --border-thick: 3px;
+    --radius-sm: 4px;
     --radius-control: 6px;
+    --radius-md: 8px;
+    --radius-lg: 10px;
     --radius-card: 12px;
+    --radius-pill: 999px;
     --control-min-height: 46px;
     --control-pad-y: 10px;
     --control-pad-x: 16px;