style(web): solid underline on the Started toggle, not dotted

Same affordance, cleaner line: solid underline tinted to the border gray at
rest (subtle, doesn't read as a broken link) and to the current text colour
on hover (more emphasis).

src/ci_orchestrator/web/static/app.css

@@ -512,10 +512,11 @@ input[type="text"], input[type="number"], select {
   margin: 0;
   font: inherit;
   cursor: pointer;
-  text-decoration: underline dotted;
+  text-decoration: underline;
+  text-decoration-color: var(--border);
   text-underline-offset: 2px;
 }
-.time-toggle:hover { color: var(--text); }
+.time-toggle:hover { color: var(--text); text-decoration-color: currentColor; }
 
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