fix(decnet_web/css): sweep rgba colour literals to tokens app-wide

Pre-this-commit, ~80 rgba() literals across 24 files were
hardcoding alert-red, warn-amber, info-cyan, panel-dark, and
white-text-with-alpha shades that bypassed the token cascade.
Net effect in light mode: the .eml/SESSREC drawers, AttackerDetail
verdict pills, MazeNET net-box headers, OPEN/REPLAY action
buttons, threat-intel cards, and all the dim 'whitish' overlays
stayed on their dark-mode hex values, producing the unreadable
panels in the screenshots.

Sweep maps each rgba colour family onto the existing token by
alpha bucket — rgba(13,17,23,*) -> var(--panel),
rgba(255,65,65,*) -> var(--alert)/-tint-10,
rgba(255,170,0,*) and rgba(224,160,64,*) -> var(--warn)/-tint-10,
rgba(0,200,255,*) -> var(--info)/-tint-10,
rgba(255,255,255,*) -> var(--fg-N)/var(--matrix-tint-N) by alpha.

VERDICT_TONE in AttackerDetail (MALICIOUS/SUSPICIOUS/BENIGN/
NO SIGNAL) was the worst offender — string literals
'#ff4d4d'/'#ffae42'/'#5fd07a'/rgba(255,255,255,0.4) baked into
inline JS styles. Now resolves at render time via var(--alert)/
var(--warn)/var(--ok)/var(--fg-4).

New tokens in :root:
 - --bg-color (alias of --bg) — drawers used this name with
   #0d1117 fallback that fired in every browser because nothing
   defined --bg-color. Adding the alias makes drawers re-tone.
 - --info / --info-tint-10 / --info-tint-30 — REPLAY buttons and
   any future neutral-secondary use.
 - --ok — semantic alias for 'verified good' (matrix in dark,
   emerald in light) so BENIGN pills stay readable across themes.

Login.css left intentionally — pre-auth surface, not themed.

decnet_web/src/index.css

@@ -14,11 +14,24 @@
 
   /* Back-compat names used across the codebase */
   --background-color: var(--bg);
+  --bg-color:         var(--bg);    /* used by drawers and other inline styles */
   --text-color:       var(--matrix);
   --accent-color:     var(--violet);
   --secondary-color:  var(--panel);
   --border-color:     var(--border);
 
+  /* Cyan/info — REPLAY buttons, neutral status that's neither
+   * "good/active" (matrix) nor "stop" (alert). */
+  --info:             #22d3ee;
+  --info-tint-10:     rgba(34, 211, 238, 0.10);
+  --info-tint-30:     rgba(34, 211, 238, 0.30);
+
+  /* Benign/healthy — semantic alias for "verified good". Stays
+   * matrix in dark, picks up a darker emerald in light so a
+   * BENIGN pill still reads as "green check" without the dark-mode
+   * neon. */
+  --ok:               var(--matrix);
+
   /* ── Foreground opacities ──────────────────────── */
   --fg-1: var(--matrix);
   --fg-2: rgba(0, 255, 65, 0.80);
@@ -151,6 +164,16 @@ html[data-theme="light"] {
   --warn-tint-10:    rgba(180, 83, 9, 0.12);
   --crit-tint-10:    rgba(185, 28, 28, 0.10);
 
+  /* Cyan/info dims to slate in light mode so REPLAY buttons read
+   * as a calm secondary against cream rather than an electric pop. */
+  --info:            #155e75;
+  --info-tint-10:    rgba(21, 94, 117, 0.10);
+  --info-tint-30:    rgba(21, 94, 117, 0.20);
+
+  /* Benign in light mode — emerald, the one "happy green" we keep,
+   * tuned dark enough to read on cream. */
+  --ok:              #047857;
+
   /* Glows no-op'd — kept defined so .btn:hover etc. don't
    * break, just produce no halo. */
   --matrix-glow:       none;