feat: add custom slug validation and handling for posts

- Enhance content configuration with slug validation to ensure only valid characters are used
- Update post routing to support custom slugs with fallback to default slug
- Implement slug duplication check to prevent conflicts across different languages
- Modify various page components to use custom or default slugs in URL generation

src/content/config.ts

@@ -11,7 +11,19 @@ const postsCollection = defineCollection({
     image: z.string().optional().default(''),
     // Extended Settings
     lang: z.string().optional().default(''),
-    slug: z.string().optional().default(''),
+    slug: z.string()
+      .optional()
+      .default('')
+      .refine(
+        (slug) => {
+          if (!slug)
+            return true
+          return /^[\w\-]*$/.test(slug)
+        },
+        {
+          message: 'Slug can only contain letters, numbers, hyphens and underscores',
+        },
+      ),
     toc: z.boolean().optional().default(false),
     pin: z.boolean().optional().default(false),
     draft: z.boolean().optional().default(false),