Add memory_limit/max_execution_time sanity checks (#106)

config/requirements.php only checked PHP version and 6 extensions. A
deployment on a host with a low default memory_limit (e.g. shared-
hosting-style 128M) passed the startup requirements check cleanly and
only surfaced as a mysterious failure under real load — a large CSV
export, an oversized dashboard query on a big install.

Added min_memory_limit_mb (256) and min_max_execution_time (30s)
thresholds to config/requirements.php, checked as warnings (not hard
failures, since a low limit doesn't break every request) in both
scripts/check_requirements.php (CI) and api/health.php (production
monitoring). -1/0 (unlimited) always passes.

Verified the ini-size parsing and warning logic directly with
low/high/unlimited memory_limit and max_execution_time values.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MGDKHiU5RJdo3dqQUDow3X

scripts/check_requirements.php

@@ -10,9 +10,30 @@
  * Usage: php scripts/check_requirements.php
  */
 
+/**
+ * Parse a php.ini size value (e.g. "128M", "1G", "-1") into bytes.
+ * Returns -1 for unlimited.
+ */
+function parseIniBytes(string $val): int
+{
+    $val = trim($val);
+    if ($val === '' || $val === '-1') {
+        return -1;
+    }
+    $unit = strtolower(substr($val, -1));
+    $num = (int)$val;
+    return match ($unit) {
+        'g' => $num * 1024 * 1024 * 1024,
+        'm' => $num * 1024 * 1024,
+        'k' => $num * 1024,
+        default => $num,
+    };
+}
+
 $req = require __DIR__ . '/../config/requirements.php';
 
 $errors = [];
+$warnings = [];
 
 // PHP version
 $minPhp = $req['min_php_version'];
@@ -27,6 +48,28 @@ foreach ($req['required_extensions'] as $ext) {
     }
 }
 
+// memory_limit / max_execution_time sanity checks (warnings, not hard
+// failures — see config/requirements.php for why these matter).
+$memLimitIni = ini_get('memory_limit');
+$memLimitBytes = parseIniBytes($memLimitIni);
+$minMemBytes = $req['min_memory_limit_mb'] * 1024 * 1024;
+if ($memLimitBytes !== -1 && $memLimitBytes < $minMemBytes) {
+    $warnings[] = sprintf(
+        'memory_limit is %s, below the recommended minimum %dM',
+        $memLimitIni,
+        $req['min_memory_limit_mb']
+    );
+}
+
+$maxExecTime = (int)ini_get('max_execution_time');
+if ($maxExecTime !== 0 && $maxExecTime < $req['min_max_execution_time']) {
+    $warnings[] = sprintf(
+        'max_execution_time is %ds, below the recommended minimum %ds',
+        $maxExecTime,
+        $req['min_max_execution_time']
+    );
+}
+
 if (!empty($errors)) {
     fwrite(STDERR, "Requirement check FAILED:\n");
     foreach ($errors as $err) {
@@ -35,6 +78,10 @@ if (!empty($errors)) {
     exit(1);
 }
 
+foreach ($warnings as $warn) {
+    fwrite(STDERR, "Requirement check WARNING: " . $warn . "\n");
+}
+
 printf(
     "Requirement check passed: PHP %s (>= %s); extensions: %s\n",
     PHP_VERSION,