feat: lab-terminal theme + new logo

Adopt the Hangman Lab visual language (adapted from the Gitea
STYLE.md, Gitea-only mechanics excluded):

- New acid SVG mark as favicon (?v cache-bust) and navbar logo.
- Single acid accent (#d8ff3e); retune globals.css tokens to the
  ink/panel/line/text/dim/danger palette; drop the cyan/violet pair
  (secondary -> same acid so existing components stay on-brand).
- Fonts: IBM Plex Mono for body/UI/mono, Major Mono Display for the
  lowercase brand lockup; Tailwind fontFamily + content fonts updated.
- Site-wide fixed 48px blueprint-grid backdrop + one acid sheen.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/Markdowns/MarkdownEditor.css

@@ -12,7 +12,7 @@
 }
 
 code {
-    font-family: ui-monospace, "JetBrains Mono", "Courier New", Courier, monospace;
+    font-family: ui-monospace, "IBM Plex Mono", "Courier New", Courier, monospace;
     background-color: hsl(var(--muted));
     color: hsl(var(--foreground));
     padding: 2px 6px;

src/components/Markdowns/MarkdownView.css

@@ -34,7 +34,7 @@
 .markdown-preview h4,
 .markdown-preview h5,
 .markdown-preview h6 {
-    font-family: "JetBrains Mono", ui-monospace, monospace;
+    font-family: "IBM Plex Mono", ui-monospace, monospace;
     font-weight: 600;
     color: hsl(var(--foreground));
     line-height: 1.3;
@@ -108,7 +108,7 @@
 
 /* Inline code */
 .markdown-preview :not(pre) > code {
-    font-family: "JetBrains Mono", ui-monospace, monospace;
+    font-family: "IBM Plex Mono", ui-monospace, monospace;
     font-size: 0.85em;
     background-color: hsl(var(--muted));
     color: hsl(var(--primary));
@@ -128,7 +128,7 @@
     box-shadow: inset 0 0 40px -20px hsl(var(--primary) / 0.25);
 }
 .markdown-preview pre code {
-    font-family: "JetBrains Mono", ui-monospace, monospace;
+    font-family: "IBM Plex Mono", ui-monospace, monospace;
     font-size: 0.85rem;
     background: transparent;
     border: none;
@@ -150,7 +150,7 @@
 }
 .markdown-preview th {
     background-color: hsl(var(--muted));
-    font-family: "JetBrains Mono", ui-monospace, monospace;
+    font-family: "IBM Plex Mono", ui-monospace, monospace;
     font-size: 0.8rem;
     text-transform: uppercase;
     letter-spacing: 0.04em;

src/components/Navigations/MainNavigation.js

@@ -124,13 +124,13 @@ const MainNavigation = () => {
                     className="group flex items-center gap-2.5 pr-3"
                 >
                     <img
-                        src="/icons/logo.png"
-                        alt="Logo"
-                        className="h-7 w-7 rounded"
+                        src="/icons/hangman-lab-logo.svg"
+                        alt="Hangman Lab"
+                        className="h-7 w-7"
                     />
-                    <span className="font-mono text-sm font-semibold tracking-tight">
-                        <span className="text-foreground">HANGMAN</span>
-                        <span className="neon-text">//LAB</span>
+                    <span className="font-display text-base leading-none tracking-tight">
+                        <span className="text-foreground">hangman</span>
+                        <span className="neon-text"> lab</span>
                     </span>
                 </Link>