v0.4.1: harden ISO uploads and beta UI polish

Add browser-safe chunked ISO uploads with progress, partial-file visibility, offset validation, and abort cleanup while keeping the legacy multipart endpoint for API clients.

Record host-log validation coverage, keep the queue/status UI copy clean, move release docs to 0.4.1, and tighten the dark theme to a near-black Netbox-style palette.

crates/webui/src/app.css

@@ -9,10 +9,10 @@
 
 :root {
   /* Jet-black dark palette (default). Modelled on Netbox Labs's
-     near-black product chrome — surfaces step from #000 → #0d → #16 → #1c
+     near-black product chrome, with surfaces stepping subtly upward
      rather than the previous blue-tinted ramp, so the UI reads as a
      genuine "dark" rather than "dim navy". */
-  --bg:           #000000;
+  --bg:           #030303;
   --bg-panel:    #0a0a0a;
   --bg-panel-2:  #141414;
   --bg-elev:     #1c1c1c;
@@ -26,7 +26,7 @@
   --ok:           #4ade80;
   --border:       #1f1f1f;
   --border-soft: #141414;
-  --terminal-bg: #000000;
+  --terminal-bg: #050505;
   --shadow-card: 0 1px 0 rgba(255,255,255,0.02), 0 8px 24px rgba(0,0,0,0.55);
   --radius:      6px;
   --radius-lg:  10px;
@@ -41,7 +41,7 @@
      consistency. Designed against Netbox Labs's reference screenshot:
      near-white surfaces, soft grey dividers, dark text. */
   --bg:           #f6f8fb;
-  --bg-panel:    #ffffff;
+  --bg-panel:    #fbfcfe;
   --bg-panel-2:  #f0f3f8;
   --bg-elev:     #e6ebf2;
   --fg:           #1c2330;
@@ -253,7 +253,7 @@ button, .btn {
   cursor: pointer;
   transition: background 0.12s ease;
 }
-button:hover, .btn:hover { background: var(--accent-dim); color: #fff; }
+button:hover, .btn:hover { background: var(--accent-dim); color: #f4fffd; }
 button.ghost { background: transparent; color: var(--fg); border: 1px solid var(--border); }
 button.ghost:hover { background: var(--bg-panel-2); color: var(--fg); }
 button.danger { background: transparent; color: var(--err); border: 1px solid color-mix(in srgb, var(--err) 35%, transparent); }