feat: add static demo site at demo.snapotter.com

- New apps/demo/ that reuses apps/web components with mocked API layer
- Full UI shell: login, change password, analytics consent, dashboard, all tool pages
- Stateful mock tracks session flow (password change, analytics consent)
- Demo banner with link to GitHub repo
- Processing attempts show info message with GitHub link
- Deployed to Cloudflare Pages as static site (no backend)

Also links demo across all surfaces:
- README: "Live Demo" badge
- Landing navbar: "Try Demo" CTA button (replaces "Book a Demo")
- Landing hero: "No sign-ups. No credit card." tagline
- Docs getting-started: "Try before installing" tip box

Other changes:
- Docs: move NVIDIA GPU section above GHCR, demote GHCR to collapsed details
- Fix before-after slider checkerboard background for transparency
- Fix remove-bg preview reset when no effects applied

apps/demo/src/styles/globals.css

@@ -0,0 +1,108 @@
+@import "tailwindcss";
+@source "../../../web/src/**/*.tsx";
+@source "../../../web/src/**/*.ts";
+
+:root {
+  font-family:
+    "Inter", ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont,
+    "Segoe UI", "Noto Sans", "Noto Sans CJK SC", "Noto Sans CJK TC",
+    "Noto Sans CJK JP", "Noto Sans CJK KR", "Noto Sans Arabic",
+    "Noto Sans Devanagari", "Noto Sans Thai", sans-serif,
+    "Apple Color Emoji", "Segoe UI Emoji";
+}
+
+@theme {
+  --color-primary: #3b82f6;
+  --color-primary-foreground: #ffffff;
+  --color-background: #ffffff;
+  --color-foreground: #0f172a;
+  --color-muted: #f1f5f9;
+  --color-muted-foreground: #64748b;
+  --color-border: #e2e8f0;
+  --color-card: #ffffff;
+  --color-card-foreground: #0f172a;
+  --color-sidebar: #f8fafc;
+  --color-sidebar-foreground: #334155;
+  --color-accent: #3b82f6;
+  --color-destructive: #ef4444;
+}
+
+.dark {
+  --color-background: #0f172a;
+  --color-foreground: #f8fafc;
+  --color-muted: #1e293b;
+  --color-muted-foreground: #94a3b8;
+  --color-border: #334155;
+  --color-card: #1e293b;
+  --color-card-foreground: #f8fafc;
+  --color-sidebar: #1e293b;
+  --color-sidebar-foreground: #cbd5e1;
+}
+
+input[type="range"] {
+  -webkit-appearance: none;
+  appearance: none;
+  height: 4px;
+  border-radius: 9999px;
+  background: var(--color-muted);
+  outline: none;
+  cursor: pointer;
+}
+
+input[type="range"]::-webkit-slider-thumb {
+  -webkit-appearance: none;
+  appearance: none;
+  width: 12px;
+  height: 12px;
+  border-radius: 50%;
+  background: var(--color-foreground);
+  cursor: pointer;
+  border: 2px solid var(--color-background);
+  box-shadow: 0 0 0 1px var(--color-border);
+  transition: transform 0.1s;
+}
+
+input[type="range"]::-webkit-slider-thumb:hover {
+  transform: scale(1.15);
+}
+
+input[type="range"]::-moz-range-thumb {
+  width: 12px;
+  height: 12px;
+  border-radius: 50%;
+  background: var(--color-foreground);
+  cursor: pointer;
+  border: 2px solid var(--color-background);
+  box-shadow: 0 0 0 1px var(--color-border);
+}
+
+input[type="range"]::-moz-range-track {
+  height: 4px;
+  border-radius: 9999px;
+  background: var(--color-muted);
+}
+
+[dir="rtl"] {
+  direction: rtl;
+  text-align: right;
+}
+
+[dir="rtl"] input[type="text"],
+[dir="rtl"] input[type="password"],
+[dir="rtl"] input[type="email"],
+[dir="rtl"] input[type="number"],
+[dir="rtl"] input[type="search"],
+[dir="rtl"] textarea,
+[dir="rtl"] select {
+  text-align: right;
+}
+
+[dir="rtl"] input[type="range"] {
+  direction: ltr;
+}
+
+[dir="rtl"] pre,
+[dir="rtl"] code {
+  direction: ltr;
+  text-align: left;
+}