fix(database): normalize read/write host lists

Trim comma-separated database host values and fall back to DB_HOST or the default host when write hosts are empty. Add unit coverage for read/write host parsing.

tests/Unit/DatabaseReadWriteHostConfigTest.php

@@ -0,0 +1,64 @@
+<?php
+
+use Illuminate\Support\Env;
+
+function databaseConfigWithEnvironment(array $overrides): array
+{
+    $keys = [
+        'DB_HOST',
+        'DB_READ_HOST',
+        'DB_WRITE_HOST',
+    ];
+
+    $repository = Env::getRepository();
+    $original = [];
+
+    foreach ($keys as $key) {
+        $original[$key] = env($key);
+        $repository->clear($key);
+    }
+
+    try {
+        foreach ($overrides as $key => $value) {
+            $repository->set($key, (string) $value);
+        }
+
+        return require __DIR__.'/../../config/database.php';
+    } finally {
+        foreach ($keys as $key) {
+            $repository->clear($key);
+
+            if ($original[$key] !== null) {
+                $repository->set($key, (string) $original[$key]);
+            }
+        }
+    }
+}
+
+it('trims and filters read hosts from comma separated values', function () {
+    $config = databaseConfigWithEnvironment([
+        'DB_READ_HOST' => ' read-1, read-2, ',
+    ]);
+
+    expect($config['connections']['pgsql']['read']['host'])->toBe(['read-1', 'read-2']);
+});
+
+it('falls back to db host when write host is empty', function () {
+    $config = databaseConfigWithEnvironment([
+        'DB_HOST' => 'primary-db',
+        'DB_READ_HOST' => 'read-db',
+        'DB_WRITE_HOST' => '',
+    ]);
+
+    expect($config['connections']['pgsql']['write']['host'])->toBe(['primary-db']);
+});
+
+it('falls back to the default host when write host and db host are empty', function () {
+    $config = databaseConfigWithEnvironment([
+        'DB_HOST' => '',
+        'DB_READ_HOST' => 'read-db',
+        'DB_WRITE_HOST' => '',
+    ]);
+
+    expect($config['connections']['pgsql']['write']['host'])->toBe(['coolify-db']);
+});