fix(decnet_web/css): three light-mode dimness fixes

--dim-color and --danger-color were referenced across drawers and
RemoteUpdates but never defined; --dim-color silently inherited
(defeating its purpose) and --danger-color fell back to literal
#f88 salmon (the 'ugly red' WifiOff icon next to UNREACHABLE
hosts). Added both as aliases in :root: --dim-color = var(--fg-3),
--danger-color = var(--alert).

--fg-2/3/4 alphas in light mode were tuned identical to dark
(0.78/0.55/0.35), but ink-on-cream needs more punch than
matrix-on-black at the same alpha — the deploy preview code
block (.code-block .comment / .key) and every dim caption
rendered too faint. Bumped to 0.88/0.70/0.50.

.maze-net-box.inactive applies opacity 0.42 + grayscale(0.7) for
the 'no traffic' signal. On cream that fades the LAN out of
visibility entirely. Override in light mode keeps the dotted
border as the dim-state cue and bumps opacity to 0.85 so the
header text stays legible.

decnet_web/src/components/MazeNET/MazeNET.css

@@ -199,6 +199,14 @@ body.maze-fullscreen .maze-shell {
   opacity: 0.42; filter: grayscale(0.7); border-style: dotted;
 }
 .maze-net-box.inactive .maze-net-box-head { color: var(--fg-3); }
+/* In light mode 0.42 + grayscale on cream makes inactive LANs
+ * disappear into the page. Keep the dotted border as the "no
+ * traffic" signal but bump opacity so the header is still
+ * legible. */
+html[data-theme="light"] .maze-net-box.inactive {
+  opacity: 0.85;
+  filter: none;
+}
 /* Optimistic placeholder for an enqueued LAN-add. Amber tint matches
  * the REAP button voice — clearly "in-flight, not committed" without
  * collapsing into the dimmed-out 'inactive' style which means the