spacetime init --template without arg prints template list and link to website (#5264)

# Description of Changes
- spacetime init --template without arg prints templates list and link
to website

# Screenshot
<img width="696" height="392" alt="screenshot"
src="https://github.com/user-attachments/assets/98e87537-554b-411b-96ab-3ceb9a6a9d45"
/>

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# API and ABI breaking changes

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corresponding GitHub label. -->

# Expected complexity level and risk
1

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# Testing

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reviewers to do,
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- [x] I tested the changes

Author: clockwork-tien

crates/cli/src/subcommands/init.rs

@@ -179,6 +179,8 @@ pub fn cli() -> clap::Command {
                 .short('t')
                 .long("template")
                 .value_name("TEMPLATE")
+                .num_args(0..=1)
+                .default_missing_value("")
                 .help("Template ID or GitHub repository (owner/repo or URL)"),
         )
         .arg(
@@ -208,6 +210,19 @@ pub async fn fetch_templates_list() -> anyhow::Result<Vec<TemplateDefinition>> {
     Ok(templates_list.templates)
 }
 
+async fn print_templates_list() -> anyhow::Result<()> {
+    let templates = fetch_templates_list().await?;
+
+    println!("{}", "Available templates:".bold());
+    for template in &templates {
+        println!("  {} - {}", template.id, template.description);
+    }
+    println!("\nCreate a project: spacetime init --template <id>");
+    println!("Browse all templates: {}", "https://spacetimedb.com/templates".cyan());
+
+    Ok(())
+}
+
 pub async fn check_and_prompt_login(config: &mut Config) -> anyhow::Result<bool> {
     if config.spacetimedb_token().is_some() {
         println!("{}", "You are logged in to SpacetimeDB.".green());
@@ -1676,6 +1691,13 @@ fn check_for_git() -> bool {
 
 pub async fn exec(mut config: Config, args: &ArgMatches) -> anyhow::Result<PathBuf> {
     let options = InitOptions::from_args(args);
+
+    // --template without arg prints templates list and link to website
+    if options.template.as_deref() == Some("") {
+        print_templates_list().await?;
+        return Ok(PathBuf::new());
+    }
+
     let is_interactive = !options.non_interactive;
     let template = options.template.as_ref();
     let server_lang = options.lang.as_ref();