diff --git a/01/backend/config/db.php b/01/backend/config/db.php
index 287e5da..67677f8 100644
--- a/01/backend/config/db.php
+++ b/01/backend/config/db.php
@@ -1,4 +1,10 @@
 <?php
+/**
+ * Singleton PDO connection.
+ *
+ * Coolify: set DB_HOST, DB_PORT, DB_DATABASE, DB_USERNAME, and DB_PASSWORD
+ * from the database service credentials.
+ */
 class Database {
     private static $conn = null;
 
@@ -9,22 +15,41 @@ class Database {
 
     public static function getConnection() {
         if (self::$conn === null) {
-            try {
+            $dbUrl = self::env('DATABASE_URL');
+            if ($dbUrl) {
+                $parsed = parse_url($dbUrl);
+                $host = $parsed['host'] ?? '127.0.0.1';
+                $port = $parsed['port'] ?? '3306';
+                $username = $parsed['user'] ?? 'root';
+                $password = $parsed['pass'] ?? '';
+                $dbName = ltrim($parsed['path'], '/');
+            } else {
                 $host = self::env('DB_HOST', '127.0.0.1');
                 $port = self::env('DB_PORT', '3306');
                 $dbName = self::env('DB_DATABASE', 'webgis_db');
                 $username = self::env('DB_USERNAME', 'root');
                 $password = self::env('DB_PASSWORD', '');
+            }
 
-                self::$conn = new PDO(
-                    "mysql:host={$host};port={$port};dbname={$dbName};charset=utf8mb4",
-                    $username,
-                    $password
-                );
-                self::$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
-                self::$conn->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
-            } catch (PDOException $exception) {
-                echo "Connection error: " . $exception->getMessage();
+            self::$conn = new PDO(
+                "mysql:host={$host};port={$port};dbname={$dbName};charset=utf8mb4",
+                $username,
+                $password
+            );
+            self::$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
+            self::$conn->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
+
+            // Disable strict mode for GROUP BY to prevent 1055 errors in Coolify's MariaDB
+            self::$conn->exec("SET SESSION sql_mode=(SELECT REPLACE(@@sql_mode,'ONLY_FULL_GROUP_BY',''))");
+
+            // Auto-initialize database if empty
+            $stmt = self::$conn->query("SHOW TABLES LIKE 'users'");
+            if ($stmt->rowCount() == 0) {
+                $sqlFile = __DIR__ . '/../../../database/webgis_db.sql';
+                if (file_exists($sqlFile)) {
+                    $sql = file_get_contents($sqlFile);
+                    self::$conn->exec($sql);
+                }
             }
         }
         return self::$conn;
diff --git a/02/backend/config/db.php b/02/backend/config/db.php
index 287e5da..67677f8 100644
--- a/02/backend/config/db.php
+++ b/02/backend/config/db.php
@@ -1,4 +1,10 @@
 <?php
+/**
+ * Singleton PDO connection.
+ *
+ * Coolify: set DB_HOST, DB_PORT, DB_DATABASE, DB_USERNAME, and DB_PASSWORD
+ * from the database service credentials.
+ */
 class Database {
     private static $conn = null;
 
@@ -9,22 +15,41 @@ class Database {
 
     public static function getConnection() {
         if (self::$conn === null) {
-            try {
+            $dbUrl = self::env('DATABASE_URL');
+            if ($dbUrl) {
+                $parsed = parse_url($dbUrl);
+                $host = $parsed['host'] ?? '127.0.0.1';
+                $port = $parsed['port'] ?? '3306';
+                $username = $parsed['user'] ?? 'root';
+                $password = $parsed['pass'] ?? '';
+                $dbName = ltrim($parsed['path'], '/');
+            } else {
                 $host = self::env('DB_HOST', '127.0.0.1');
                 $port = self::env('DB_PORT', '3306');
                 $dbName = self::env('DB_DATABASE', 'webgis_db');
                 $username = self::env('DB_USERNAME', 'root');
                 $password = self::env('DB_PASSWORD', '');
+            }
 
-                self::$conn = new PDO(
-                    "mysql:host={$host};port={$port};dbname={$dbName};charset=utf8mb4",
-                    $username,
-                    $password
-                );
-                self::$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
-                self::$conn->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
-            } catch (PDOException $exception) {
-                echo "Connection error: " . $exception->getMessage();
+            self::$conn = new PDO(
+                "mysql:host={$host};port={$port};dbname={$dbName};charset=utf8mb4",
+                $username,
+                $password
+            );
+            self::$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
+            self::$conn->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
+
+            // Disable strict mode for GROUP BY to prevent 1055 errors in Coolify's MariaDB
+            self::$conn->exec("SET SESSION sql_mode=(SELECT REPLACE(@@sql_mode,'ONLY_FULL_GROUP_BY',''))");
+
+            // Auto-initialize database if empty
+            $stmt = self::$conn->query("SHOW TABLES LIKE 'users'");
+            if ($stmt->rowCount() == 0) {
+                $sqlFile = __DIR__ . '/../../../database/webgis_db.sql';
+                if (file_exists($sqlFile)) {
+                    $sql = file_get_contents($sqlFile);
+                    self::$conn->exec($sql);
+                }
             }
         }
         return self::$conn;
diff --git a/03/backend/config/db.php b/03/backend/config/db.php
index 287e5da..67677f8 100644
--- a/03/backend/config/db.php
+++ b/03/backend/config/db.php
@@ -1,4 +1,10 @@
 <?php
+/**
+ * Singleton PDO connection.
+ *
+ * Coolify: set DB_HOST, DB_PORT, DB_DATABASE, DB_USERNAME, and DB_PASSWORD
+ * from the database service credentials.
+ */
 class Database {
     private static $conn = null;
 
@@ -9,22 +15,41 @@ class Database {
 
     public static function getConnection() {
         if (self::$conn === null) {
-            try {
+            $dbUrl = self::env('DATABASE_URL');
+            if ($dbUrl) {
+                $parsed = parse_url($dbUrl);
+                $host = $parsed['host'] ?? '127.0.0.1';
+                $port = $parsed['port'] ?? '3306';
+                $username = $parsed['user'] ?? 'root';
+                $password = $parsed['pass'] ?? '';
+                $dbName = ltrim($parsed['path'], '/');
+            } else {
                 $host = self::env('DB_HOST', '127.0.0.1');
                 $port = self::env('DB_PORT', '3306');
                 $dbName = self::env('DB_DATABASE', 'webgis_db');
                 $username = self::env('DB_USERNAME', 'root');
                 $password = self::env('DB_PASSWORD', '');
+            }
 
-                self::$conn = new PDO(
-                    "mysql:host={$host};port={$port};dbname={$dbName};charset=utf8mb4",
-                    $username,
-                    $password
-                );
-                self::$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
-                self::$conn->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
-            } catch (PDOException $exception) {
-                echo "Connection error: " . $exception->getMessage();
+            self::$conn = new PDO(
+                "mysql:host={$host};port={$port};dbname={$dbName};charset=utf8mb4",
+                $username,
+                $password
+            );
+            self::$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
+            self::$conn->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
+
+            // Disable strict mode for GROUP BY to prevent 1055 errors in Coolify's MariaDB
+            self::$conn->exec("SET SESSION sql_mode=(SELECT REPLACE(@@sql_mode,'ONLY_FULL_GROUP_BY',''))");
+
+            // Auto-initialize database if empty
+            $stmt = self::$conn->query("SHOW TABLES LIKE 'users'");
+            if ($stmt->rowCount() == 0) {
+                $sqlFile = __DIR__ . '/../../../database/webgis_db.sql';
+                if (file_exists($sqlFile)) {
+                    $sql = file_get_contents($sqlFile);
+                    self::$conn->exec($sql);
+                }
             }
         }
         return self::$conn;