Block dotfile access, remove custom CSS, fix cron npm install

- nginx: deny all requests to hidden files (/.git/config was publicly readable)
- nginx: remove CSS injection and /custom/ static file serving
- cron: install script deps at build time into /opt to avoid ro mount conflict
- docker-compose: widen cron build context for package.json COPY
- Delete unused theme/ghost-guild.css

theme/ghost-guild.css

@@ -1,61 +0,0 @@
-/*
- * 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;
-}