Replace Nuxt wiki with Outline deployment config

Strip the Nuxt 4 static site and replace with Docker Compose config
for self-hosted Outline wiki (Outline + PostgreSQL 16 + Redis 7).
Adds nginx reverse proxy with WebSocket support and CSS injection,
migration script for existing markdown articles, backup script,
and starter theme CSS.

theme/ghost-guild.css

@@ -0,0 +1,61 @@
+/*
+ * Ghost Guild — Outline Wiki Custom Theme
+ *
+ * Injected via nginx sub_filter into every Outline page.
+ * Served from /custom/ghost-guild.css.
+ *
+ * NOTE: Outline's internal class names and DOM structure may change between
+ * versions. After upgrading Outline, verify these selectors still work.
+ */
+
+/* ---------------------------------------------------------------------------
+   Brand color overrides
+   --------------------------------------------------------------------------- */
+:root {
+  --ghost-guild-primary: #2563eb;
+  --ghost-guild-bg: #fafafa;
+  --ghost-guild-text: #1a1a2e;
+}
+
+/* ---------------------------------------------------------------------------
+   Hide Outline branding
+   --------------------------------------------------------------------------- */
+
+/* "Built with Outline" footer link */
+a[href="https://www.getoutline.com"] {
+  display: none !important;
+}
+
+/* Outline logo in sidebar */
+[data-testid="sidebar-logo"],
+a[href="/"] > svg {
+  /* Replace with Ghost Guild logo via background-image if desired:
+     background-image: url(/custom/logo.svg);
+     background-size: contain;
+     background-repeat: no-repeat;
+  */
+}
+
+/* ---------------------------------------------------------------------------
+   Typography
+   --------------------------------------------------------------------------- */
+
+/* Placeholder: uncomment and update with Ghost Guild fonts
+@font-face {
+  font-family: "GhostGuild";
+  src: url("/custom/fonts/ghost-guild.woff2") format("woff2");
+  font-weight: 400;
+  font-style: normal;
+  font-display: swap;
+}
+*/
+
+/* ---------------------------------------------------------------------------
+   Layout adjustments
+   --------------------------------------------------------------------------- */
+
+/* Widen the document area slightly */
+.document-editor,
+[class*="DocumentEditor"] {
+  max-width: 48rem;
+}