feat: add configurable timeout for public database TCP proxy

Adds a per-database 'Proxy Timeout' setting for publicly exposed databases.
The nginx stream proxy_timeout can now be configured in the UI, defaulting
to 3600s (1 hour) instead of nginx's 10min default. Set to 0 for no timeout.

Fixes #7743

app/Models/ServiceDatabase.php

@@ -11,6 +11,10 @@ class ServiceDatabase extends BaseModel
 
     protected $guarded = [];
 
+    protected $casts = [
+        'public_port_timeout' => 'integer',
+    ];
+
     protected static function booted()
     {
         static::deleting(function ($service) {