Revert "fix: allow [homarr_base] template variables in app href validation (#6508)"

This reverts commit f1b7a5146a.

packages/validation/src/app.ts

@@ -5,10 +5,6 @@ export const appHrefSchema = z
   .trim()
   .url()
   .regex(/^(?!javascript)[a-zA-Z]*:\/\//i) // javascript: is not allowed, i for case insensitive (so Javascript: is also not allowed)
-  .or(z.string().trim().includes("[homarr_base]"))
-  .or(z.string().trim().includes("[homarr_hostname]"))
-  .or(z.string().trim().includes("[homarr_domain]"))
-  .or(z.string().trim().includes("[homarr_protocol]"))
   .or(z.literal(""))
   .transform((value) => (value.length === 0 ? null : value))
   .nullable();