Neutral graphite theme; branded updater icon

Coloring: the base surfaces were green-tinted darks, which read as a
green-hued background rather than green highlights. Shift the whole
surface ramp to neutral graphite (slightly cool, and lighter overall)
and keep green strictly for highlights — brand, buttons, switches,
status dots and pills, sync bars, focus rings.

- Tokens: bg #17191d, surface #1c1f24, card #23272c, hover #292e34,
  elevated #26292e, inset #121417; text neutrals #e9edec/#a9b0b3/
  #7a8388. Accent, borders, radii, shadows unchanged.
- Remove the green ambient radial washes behind the app (and login).
- Reboot / security-reset overlay gradients neutralized.

Updater icon: restore the repo's branded Sovran updater icon
(/static/icons/update.svg, true colors) in the sidebar Update System
row and in the update dialog header, replacing the generic refresh
glyph. The rebuild dialog keeps its glyph chip (no branded icon
exists for it).

app/sovran_systemsos_web/static/css/base.css

@@ -17,17 +17,17 @@
   color-scheme: dark;
 
   /* ── The Hub palette ─────────────────────────────────────────── */
-  --bg:            #141a16;
-  --surface:       #181f1b;
-  --card:          #1e2621;
-  --card-hover:    #232d27;
-  --elevated:      #212925;
-  --inset:         #121814;
+  --bg:            #17191d;
+  --surface:       #1c1f24;
+  --card:          #23272c;
+  --card-hover:    #292e34;
+  --elevated:      #26292e;
+  --inset:         #121417;
   --border:        rgba(255, 255, 255, 0.07);
   --border-strong: rgba(255, 255, 255, 0.14);
-  --text:          #e3ede7;
-  --text-2:        #a8bcb0;
-  --text-3:        #6e8578;
+  --text:          #e9edec;
+  --text-2:        #a9b0b3;
+  --text-3:        #7a8388;
   --accent:        #3ecf8e;
   --accent-strong: #42f39a;
   --accent-deep:   #1aa45d;
@@ -73,18 +73,6 @@ body {
   overflow: hidden;
 }
 
-/* Soft brand wash so the canvas never reads flat-black */
-body::before {
-  content: "";
-  position: fixed;
-  inset: 0;
-  background:
-    radial-gradient(1100px 520px at 16% -12%, rgba(66, 243, 154, 0.04), transparent 60%),
-    radial-gradient(900px 600px at 110% 110%, rgba(26, 169, 110, 0.05), transparent 55%);
-  pointer-events: none;
-  z-index: 0;
-}
-
 button { font-family: inherit; }
 
 ::selection { background: rgba(66, 243, 154, 0.25); }

app/sovran_systemsos_web/static/css/modals.css

@@ -1306,7 +1306,7 @@
   position: fixed;
   inset: 0;
   z-index: 300;
-  background: radial-gradient(1000px 640px at 50% 18%, #17211c, #0b100d 72%);
+  background: radial-gradient(1000px 640px at 50% 18%, #202429, #0f1113 72%);
   display: flex;
   align-items: center;
   justify-content: center;

app/sovran_systemsos_web/static/css/security.css

@@ -221,7 +221,7 @@
   display: none;
   position: fixed;
   inset: 0;
-  background: radial-gradient(1000px 640px at 50% 18%, #17211c, #0b100d 72%);
+  background: radial-gradient(1000px 640px at 50% 18%, #202429, #0f1113 72%);
   z-index: 1000;
   align-items: center;
   justify-content: center;