refactor: move blog from EmDash to Astro content collections

EmDash CMS integration is being removed. The blog content is
moved to native Astro content collections (markdown files in
src/content/blog/) which works with the static output config.

Changes:
- Remove EmDash from astro.config.mjs (revert to static output)
- Remove emdash packages from package.json/package-lock.json
- Remove seed/seed.json (was EmDash-only)
- Remove src/live.config.ts (EmDash Astro loader)
- Add src/content.config.ts (Astro content collection for blog)
- Move 3 blog posts to src/content/blog/*.md
- Update src/pages/index.astro to use getCollection('blog')
- Update src/pages/บทความ/[slug].astro to use render() from astro:content
  (Astro 6 API: render(article), not article.render())
- Update src/pages/บทความ/index.astro (blog list)
- Add .hermes/ to .gitignore

Verified:
- npm run build: 35 pages, complete in 2.50s
- / , /aeroflex, /about-us, /บทความ, /บทความ/welcome-post: all 200

astro.config.mjs

@@ -1,10 +1,6 @@
 import { defineConfig } from 'astro/config'
 import tailwindcss from '@tailwindcss/vite'
-import node from '@astrojs/node'
 import react from '@astrojs/react'
-import emdash, { local } from 'emdash/astro'
-import { sqlite } from 'emdash/db'
-import { google } from 'emdash/auth/providers/google'
 import { fileURLToPath } from 'url'
 import path from 'path'
 
@@ -12,10 +8,7 @@ const __dirname = path.dirname(fileURLToPath(import.meta.url))
 
 export default defineConfig({
   site: 'https://dealplustech.com',
-  output: 'server',
-  adapter: node({
-    mode: 'standalone',
-  }),
+  output: 'static',
   vite: {
     plugins: [tailwindcss()],
     resolve: {
@@ -29,14 +22,6 @@ export default defineConfig({
   },
   integrations: [
     react(),
-    emdash({
-      database: sqlite({ url: 'file:./data.db' }),
-      storage: local({
-        directory: './uploads',
-        baseUrl: '/_emdash/api/media/file',
-      }),
-      authProviders: [google()],
-    }),
   ],
   build: {
     assets: '_assets',