feat(website): brand layer — teal palette, table logo, wordmark, footer

Anchor the site to the product's identity (Phase B branding):
- Accent palette mapped to the app's in-TUI teal (--sl-color-accent-*,
  light + dark); trim the splash hero's oversized desktop bottom padding.
- Header logo: a database-table glyph with a teal primary-key cell
  (light/dark variants); favicon redrawn to match.
- Landing wordmark 'RELational PLAYground': teal picks out REL+PLAY
  ('relplay', the domain) and R/D/B/M/S (spelling out RDBMS). Sizes
  locked in em off one master scale so the lockup zooms as a rigid unit.
- Footer override: default footer + an understated company (Lazy
  Evaluation Ltd) and source/issues line.

No engine names or 'DSL' in user-facing copy.

website/src/components/Footer.astro

@@ -0,0 +1,44 @@
+---
+/**
+ * Footer override: render Starlight's default footer (pagination, last-updated,
+ * "Built with Starlight"), then append a small, understated brand line — the
+ * company (linked to its disclosures) and an unobtrusive source/issues link
+ * (true to "people can join in, but don't advertise it loudly").
+ */
+import Default from '@astrojs/starlight/components/Footer.astro';
+---
+
+<Default><slot /></Default>
+
+<div class="relplay-footer">
+	<p>
+		Made by <a href="https://www.lazyevaluation.biz/">Lazy Evaluation Ltd</a>
+		<span class="sep">·</span>
+		<a href="https://git.lazyeval.net/oli/rdbms-playground">Source &amp; issues</a>
+	</p>
+</div>
+
+<style>
+	.relplay-footer {
+		margin-top: 1rem;
+		padding-top: 1rem;
+		border-top: 1px solid var(--sl-color-hairline);
+	}
+	.relplay-footer p {
+		margin: 0;
+		font-size: var(--sl-text-xs);
+		color: var(--sl-color-gray-3);
+	}
+	.relplay-footer a {
+		color: var(--sl-color-gray-2);
+		text-decoration: none;
+	}
+	.relplay-footer a:hover {
+		color: var(--sl-color-text-accent);
+		text-decoration: underline;
+	}
+	.relplay-footer .sep {
+		margin: 0 0.4rem;
+		opacity: 0.6;
+	}
+</style>