Improve diagnosis: check .htaccess even when error_log exists

Problem: Only diagnosing 4 unique issues out of 7555 errors because script
was only checking .htaccess when error_log didn't exist. Most errors had
error_log files but no matching PHP errors, so fell through to
"NO_PHP_ERROR_LOGGED" without further investigation.

Solution: Added fallback .htaccess checking in two scenarios:
1. When error_log exists but has no matching errors for this URL
2. When error_log exists but grep finds no relevant PHP errors

Now checks for common .htaccess issues in all cases:
- Invalid php_value/php_flag directives (incompatible with FPM)
- Malformed RewriteRule syntax

This should dramatically increase the number of diagnosed issues by catching
.htaccess problems even when PHP error_log exists.

modules/website/500-error-tracker.sh

@@ -349,10 +349,68 @@ while IFS='|' read -r domain user status url timestamp ip; do
                 ((diagnosed_causes["$cause"]++))
                 [ -z "${cause_examples[$cause]}" ] && cause_examples["$cause"]="$diagnosis"
             else
-                ((diagnosed_causes["NO_PHP_ERROR_LOGGED"]++))
+                # No matching error in error_log - check .htaccess as fallback
+                if [ "$user" != "unknown" ] && [ -f "$docroot/.htaccess" ]; then
+                    htaccess_file="$docroot/.htaccess"
+                    htaccess_issues=""
+
+                    # Check for invalid PHP directives
+                    if grep -qE "^[[:space:]]*(php_value|php_flag|php_admin_value|php_admin_flag)" "$htaccess_file" 2>/dev/null; then
+                        if ! apache2ctl -M 2>/dev/null | grep -q "php.*module"; then
+                            htaccess_issues="PHP directives (php_value/php_flag) incompatible with current PHP handler (not mod_php)"
+                        fi
+                    fi
+
+                    # Check for malformed RewriteRule
+                    bad_rewrite=$(grep -nE "RewriteRule.*\[.*[^]]*$" "$htaccess_file" 2>/dev/null | head -1)
+                    if [ -n "$bad_rewrite" ]; then
+                        htaccess_issues="${htaccess_issues:+$htaccess_issues; }Malformed RewriteRule: $bad_rewrite"
+                    fi
+
+                    if [ -n "$htaccess_issues" ]; then
+                        cause="HTACCESS_ERROR"
+                        diagnosis="$domain$url - .htaccess error: $htaccess_issues"
+                        echo "$cause|$diagnosis" >> "$DETAILED_DIAGNOSIS"
+                        ((diagnosed_causes["$cause"]++))
+                        [ -z "${cause_examples[$cause]}" ] && cause_examples["$cause"]="$diagnosis"
+                    else
+                        ((diagnosed_causes["NO_PHP_ERROR_LOGGED"]++))
+                    fi
+                else
+                    ((diagnosed_causes["NO_PHP_ERROR_LOGGED"]++))
+                fi
             fi
         else
-            ((diagnosed_causes["NO_PHP_ERROR_LOGGED"]++))
+            # No error in error_log at all - check .htaccess
+            if [ "$user" != "unknown" ] && [ -f "$docroot/.htaccess" ]; then
+                htaccess_file="$docroot/.htaccess"
+                htaccess_issues=""
+
+                # Check for invalid PHP directives
+                if grep -qE "^[[:space:]]*(php_value|php_flag|php_admin_value|php_admin_flag)" "$htaccess_file" 2>/dev/null; then
+                    if ! apache2ctl -M 2>/dev/null | grep -q "php.*module"; then
+                        htaccess_issues="PHP directives (php_value/php_flag) incompatible with current PHP handler (not mod_php)"
+                    fi
+                fi
+
+                # Check for malformed RewriteRule
+                bad_rewrite=$(grep -nE "RewriteRule.*\[.*[^]]*$" "$htaccess_file" 2>/dev/null | head -1)
+                if [ -n "$bad_rewrite" ]; then
+                    htaccess_issues="${htaccess_issues:+$htaccess_issues; }Malformed RewriteRule: $bad_rewrite"
+                fi
+
+                if [ -n "$htaccess_issues" ]; then
+                    cause="HTACCESS_ERROR"
+                    diagnosis="$domain$url - .htaccess error: $htaccess_issues"
+                    echo "$cause|$diagnosis" >> "$DETAILED_DIAGNOSIS"
+                    ((diagnosed_causes["$cause"]++))
+                    [ -z "${cause_examples[$cause]}" ] && cause_examples["$cause"]="$diagnosis"
+                else
+                    ((diagnosed_causes["NO_PHP_ERROR_LOGGED"]++))
+                fi
+            else
+                ((diagnosed_causes["NO_PHP_ERROR_LOGGED"]++))
+            fi
         fi
     else
         # No error log found - check .htaccess and permissions thoroughly