Improve diagnostics display: group by issue pattern, not by domain

Problem: Showing 86 "unique issues" when actually many domains have the
same .htaccess error was overwhelming and hard to read. For example,
14 airmarkoverhaul.com subdomains all had identical .htaccess issues.

Solution: Reorganize to group by issue pattern, showing affected domains:

New format:
  Issue: PHP directives incompatible with FPM; Malformed RewriteRule...
  Affected (14): airmarkengines.com, airmarkinc.com, airmarkoh.com, ...

Benefits:
- Shows actual unique issue patterns (not domain+issue combos)
- Lists up to 5 affected domains per issue
- Shows domain count for each issue pattern
- Limits to 10 issue patterns per cause type
- Much more readable and actionable

Instead of scrolling through 86 nearly-identical lines, you now see
the unique problems and which domains are affected by each.

modules/website/500-error-tracker.sh

@@ -743,28 +743,60 @@ echo " SPECIFIC DIAGNOSTICS (per URL/file)"
 echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
 echo ""
 
-# Show detailed diagnostics grouped by cause - deduplicate by domain+url+issue
+# Show detailed diagnostics grouped by cause and issue pattern
 if [ -f "$DETAILED_DIAGNOSIS" ] && [ -s "$DETAILED_DIAGNOSIS" ]; then
     for cause_type in PHP_MEMORY_EXHAUSTED PERMISSION_ERROR HTACCESS_ERROR PHP_FATAL_ERROR PHP_SYNTAX_ERROR MISSING_PHP_FUNCTION DATABASE_CONNECTION FILE_NOT_FOUND PHP_HANDLER_ERROR WP_DEBUG_ERROR DOCROOT_MISSING; do
-        # Get unique diagnostics (deduplicate identical domain+issue combinations)
-        unique_diags=$(grep "^${cause_type}|" "$DETAILED_DIAGNOSIS" 2>/dev/null | cut -d'|' -f2 | sort -u)
-        cause_count=$(echo "$unique_diags" | grep -c "^" 2>/dev/null || echo "0")
 
-        if [ "$cause_count" -gt 0 ] && [ -n "$unique_diags" ]; then
+        cause_count=$(grep -c "^${cause_type}|" "$DETAILED_DIAGNOSIS" 2>/dev/null || echo "0")
+
+        if [ "$cause_count" -gt 0 ]; then
             cause_display=$(echo "$cause_type" | tr '_' ' ')
-            echo -e "${RED}${BOLD}$cause_display ($cause_count unique issues)${NC}"
+            echo -e "${RED}${BOLD}$cause_display ($cause_count occurrences)${NC}"
             echo ""
 
-            echo "$unique_diags" | head -20 | while read -r diag_line; do
-                [ -z "$diag_line" ] && continue
-                echo -e "  ${YELLOW}•${NC} $diag_line"
+            # Group by unique error pattern (not domain)
+            declare -A issue_domains
+
+            while IFS='|' read -r ctype full_diag; do
+                # Extract just the error part (after domain/)
+                issue_pattern=$(echo "$full_diag" | sed 's/^[^ ]* - //')
+                domain_part=$(echo "$full_diag" | grep -oP '^[^/]+')
+
+                # Group domains with same issue
+                if [ -z "${issue_domains[$issue_pattern]}" ]; then
+                    issue_domains[$issue_pattern]="$domain_part"
+                else
+                    # Count how many domains (limit to first 5)
+                    count=$(echo "${issue_domains[$issue_pattern]}" | tr ',' '\n' | wc -l)
+                    if [ "$count" -lt 5 ]; then
+                        issue_domains[$issue_pattern]="${issue_domains[$issue_pattern]},$domain_part"
+                    elif [ "$count" -eq 5 ]; then
+                        issue_domains[$issue_pattern]="${issue_domains[$issue_pattern]},..."
+                    fi
+                fi
+            done < <(grep "^${cause_type}|" "$DETAILED_DIAGNOSIS" 2>/dev/null)
+
+            # Display grouped issues
+            shown=0
+            for pattern in "${!issue_domains[@]}"; do
+                [ $shown -ge 10 ] && break
+                ((shown++))
+
+                domains="${issue_domains[$pattern]}"
+                domain_count=$(echo "$domains" | tr ',' '\n' | grep -v '^\.\.\.$' | wc -l)
+
+                echo -e "  ${YELLOW}Issue:${NC} $pattern"
+                echo -e "  ${DIM}Affected ($domain_count):${NC} ${domains//,/, }"
+                echo ""
             done
 
-            if [ "$cause_count" -gt 20 ]; then
-                remaining=$((cause_count - 20))
-                echo -e "  ${DIM}... and $remaining more${NC}"
+            if [ "${#issue_domains[@]}" -gt 10 ]; then
+                remaining=$((${#issue_domains[@]} - 10))
+                echo -e "  ${DIM}... and $remaining more issue patterns${NC}"
+                echo ""
             fi
-            echo ""
+
+            unset issue_domains
         fi
     done
 else