feat: add clerk auth support with convex (#548)

apps/web/content/docs/cli/options.mdx

@@ -217,16 +217,24 @@ create-better-t-stack --frontend none
 
 ## Authentication
 
-### `--auth / --no-auth`
+### `--auth <provider>`
 
-Include or exclude authentication setup using Better-Auth.
+Choose authentication provider:
+
+- `better-auth`: Better-Auth authentication (default)
+- `clerk`: Clerk authentication (only with Convex backend)
+- `none`: No authentication
 
 ```bash
-create-better-t-stack --auth
-create-better-t-stack --no-auth
+create-better-t-stack --auth better-auth
+create-better-t-stack --auth clerk
+create-better-t-stack --auth none
 ```
 
-**Note:** Authentication requires both a database and backend framework to be selected. It is automatically disabled when using Convex backend or when no backend is selected.
+**Note:** 
+- `better-auth` requires both a database and backend framework
+- `clerk` is only available with Convex backend
+- Authentication is automatically set to `none` when using `--backend none` or `--database none` (unless using Convex)
 
 ## Addons
 
@@ -312,7 +320,7 @@ create-better-t-stack \
   --runtime bun \
   --frontend tanstack-router \
   --api trpc \
-  --auth \
+  --auth better-auth \
   --addons pwa biome \
   --examples todo \
   --package-manager bun \