Add CI lint configs (html-validate, linkinator), fix nav a11y and URL routing

- .htmlvalidate.json with relaxed rules for design-system inline styles
- linkinator.config.json skipping mail, external auth/platform origins
- Fix lint:html npm script quoting for Windows-shell compatibility
- Switch astro build.format to 'directory' so /pricing resolves without MultiViews
- trailingSlash: 'ignore' lets both /pricing and /pricing/ work naturally
- Add aria-label to both <nav> landmarks (Primary, Footer) to satisfy html-validate

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

astro.config.mjs

@@ -4,9 +4,11 @@ import tailwind from '@astrojs/tailwind';
 export default defineConfig({
   site: 'https://www.cameleer.io',
   output: 'static',
-  trailingSlash: 'never',
+  trailingSlash: 'ignore',
   build: {
-    format: 'file',
+    // 'directory' outputs <page>/index.html so extensionless URLs like /pricing
+    // resolve natively under Apache without MultiViews or rewrite rules.
+    format: 'directory',
     assets: 'assets',
     inlineStylesheets: 'auto',
   },