potential fix for logging on server

lib/api_log.php

@@ -10,7 +10,8 @@
  *   - web_change:   POST/PUT/PATCH/DELETE from the management website (incl. translation labels)
  *   - web_export:   Website downloads (CSV/ZIP/JSON exports, translation bundle)
  *
- * Set QDB_API_LOG=0 to disable. Logs live under logs/api/ (gitignored).
+ * Set QDB_API_LOG=0 to disable. Set QDB_API_LOG_DIR for a custom path.
+ * Default directory is uploads/logs/api (writable by PHP alongside the database).
  */
 
 /** @var list<string> */
@@ -28,11 +29,98 @@ function qdb_api_log_enabled(): bool
 
 function qdb_api_log_dir(): string
 {
+    static $resolved = null;
+    if ($resolved !== null) {
+        return $resolved;
+    }
+
     $custom = qdb_env_get('QDB_API_LOG_DIR');
     if ($custom !== null && $custom !== '') {
-        return rtrim($custom, '/\\');
+        $resolved = rtrim($custom, '/\\');
+        return $resolved;
     }
-    return dirname(__DIR__) . '/logs/api';
+
+    $root = dirname(__DIR__);
+    foreach ([$root . '/uploads/logs/api', $root . '/logs/api'] as $candidate) {
+        if (qdb_api_log_dir_is_usable($candidate)) {
+            $resolved = $candidate;
+            return $resolved;
+        }
+    }
+
+    $resolved = $root . '/uploads/logs/api';
+    return $resolved;
+}
+
+function qdb_api_log_dir_is_usable(string $dir): bool
+{
+    if (is_dir($dir)) {
+        return is_writable($dir);
+    }
+    $parent = dirname($dir);
+    if (is_dir($parent) && is_writable($parent)) {
+        return true;
+    }
+    if (@mkdir($dir, 0775, true)) {
+        return is_writable($dir);
+    }
+    return is_dir($dir) && is_writable($dir);
+}
+
+/**
+ * Diagnostics for admin UI (permissions, path, enabled flag).
+ *
+ * @return array<string, mixed>
+ */
+function qdb_api_log_status(): array
+{
+    $dir     = qdb_api_log_dir();
+    $enabled = qdb_api_log_enabled();
+    $exists  = is_dir($dir);
+    $writable = false;
+    $probeError = null;
+
+    if ($enabled) {
+        if (!$exists) {
+            if (!@mkdir($dir, 0775, true)) {
+                $probeError = 'Cannot create directory: ' . $dir;
+            }
+            $exists = is_dir($dir);
+        }
+        if ($exists && !is_writable($dir)) {
+            $probeError = 'Directory exists but is not writable by PHP: ' . $dir;
+        } elseif ($exists) {
+            $probe = $dir . '/.write_probe';
+            if (@file_put_contents($probe, (string)time() . "\n", LOCK_EX) === false) {
+                $probeError = 'Cannot write files in: ' . $dir;
+            } else {
+                $writable = true;
+                @unlink($probe);
+            }
+        }
+    }
+
+    $phpUser = null;
+    if (function_exists('posix_geteuid') && function_exists('posix_getpwuid')) {
+        $info = posix_getpwuid(posix_geteuid());
+        if (is_array($info) && !empty($info['name'])) {
+            $phpUser = (string)$info['name'];
+        }
+    }
+
+    return [
+        'enabled'    => $enabled,
+        'dir'        => $dir,
+        'exists'     => $exists,
+        'writable'   => $writable,
+        'error'      => $probeError,
+        'php_user'   => $phpUser,
+        'fix_hint'   => $writable || !$enabled
+            ? null
+            : 'On the server run: mkdir -p ' . $dir . ' && chown -R www-data:www-data '
+                . dirname($dir) . ' && chmod -R 775 ' . dirname($dir)
+                . ' (adjust www-data to your PHP user). Or set QDB_API_LOG_DIR in .env to a writable path.',
+    ];
 }
 
 function qdb_api_log_max_bytes(): int
@@ -421,13 +509,24 @@ function qdb_api_log_change_scalar(mixed $v): string|int|float|bool|null
 function qdb_api_log_append_line(string $line): void
 {
     $dir = qdb_api_log_dir();
-    if (!is_dir($dir) && !@mkdir($dir, 0755, true) && !is_dir($dir)) {
-        throw new RuntimeException("Cannot create log directory: $dir");
+    if (!is_dir($dir) && !@mkdir($dir, 0775, true) && !is_dir($dir)) {
+        $err = error_get_last();
+        throw new RuntimeException(
+            'Cannot create log directory: ' . $dir
+            . ($err ? ' (' . ($err['message'] ?? '') . ')' : '')
+        );
+    }
+    if (!is_writable($dir)) {
+        throw new RuntimeException('Log directory not writable: ' . $dir);
     }
 
     $path = qdb_api_log_resolve_write_path($dir);
     if (@file_put_contents($path, $line, FILE_APPEND | LOCK_EX) === false) {
-        throw new RuntimeException("Cannot write API log: $path");
+        $err = error_get_last();
+        throw new RuntimeException(
+            'Cannot write API log: ' . $path
+            . ($err ? ' (' . ($err['message'] ?? '') . ')' : '')
+        );
     }
 }
 
@@ -507,6 +606,7 @@ function qdb_api_log_read_entries(string $date, string $activityFilter = '', int
         'files'     => array_map('basename', $files),
         'truncated' => $truncated,
         'kinds'     => QDB_API_LOG_ACTIVITIES,
+        'logStatus' => qdb_api_log_status(),
     ];
 }