docs: upgrade docs site to Astro 6 and update Node.js prerequisites (#244)

Upgrades the docs site from Astro 5/Starlight 0.37 to Astro 6/Starlight 0.38.
Adds Cloudflare adapter for deployment. Updates Node.js prerequisites
across all docs to match Astro 6's requirement of v22.12.0+.
Bumps catalog versions for @astrojs/cloudflare and wrangler.

docs/src/content/docs/deployment/nodejs.mdx

@@ -5,11 +5,11 @@ description: Deploy EmDash to any Node.js hosting platform.
 
 import { Aside, Steps, Tabs, TabItem } from "@astrojs/starlight/components";
 
-EmDash runs on any Node.js 18+ hosting platform. This guide covers deployment to common providers using SQLite and local or S3-compatible storage.
+EmDash runs on any Node.js 22+ hosting platform. This guide covers deployment to common providers using SQLite and local or S3-compatible storage.
 
 ## Prerequisites
 
-- Node.js 18.17.1 or higher
+- Node.js v22.12.0 or higher
 - A Node.js hosting provider or VPS
 
 ## Configuration
@@ -91,14 +91,14 @@ export default defineConfig({
 Create a `Dockerfile`:
 
 ```dockerfile title="Dockerfile"
-FROM node:20-alpine AS builder
+FROM node:22-alpine AS builder
 WORKDIR /app
 COPY package*.json ./
 RUN npm ci
 COPY . .
 RUN npm run build
 
-FROM node:20-alpine
+FROM node:22-alpine
 WORKDIR /app
 COPY --from=builder /app/dist ./dist
 COPY --from=builder /app/node_modules ./node_modules

docs/src/content/docs/getting-started.mdx

@@ -11,7 +11,7 @@ This guide walks you through creating your first EmDash site, from installation
 
 ## Prerequisites
 
-- **Node.js** 18.17.1 or higher
+- **Node.js** v22.12.0 or higher (odd-numbered versions are not supported)
 - **npm**, **pnpm**, or **yarn**
 - A code editor (VS Code recommended)