feat: redesign server startup around Run options

Replace the old RunShutdown and RunTLS style entry points with a single Run(opts...) API for v1. Add focused startup semantics tests, keep TLS and graceful shutdown independent, ensure sibling servers are cleaned up on startup failure, and update docs to match the new option-based startup model.

docs/routing.md

@@ -142,7 +142,7 @@ func main() {
     r := touka.Default()
     fsroot, _ := fs.Sub(content, "dist")
     r.StaticFS("/", http.FS(fsroot))
-    r.Run(":8080")
+    r.Run(touka.WithAddr(":8080"))
 }
 ```