Fix notifications 500 (audit_id column), smart resolution time units

- notifications.php: audit_log PK is audit_id not log_id; alias all
  three queries with audit_id AS log_id to fix 500 error
- DashboardView: avg resolution time now picks best unit automatically
  (min < 1h, hr < 48h, days < 14d, wks otherwise) with full hours
  shown in title tooltip; adds lt-stat-unit CSS for the suffix

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

assets/css/dashboard.css

@@ -8,6 +8,14 @@
   margin-bottom: 1rem;
 }
 
+/* Unit suffix on resolution time stat (smaller, muted) */
+.lt-stat-unit {
+  font-size: 0.65em;
+  font-weight: 500;
+  margin-left: 0.15em;
+  opacity: 0.75;
+}
+
 /* Priority row highlights */
 .lt-row-critical td {
   background: rgba(255, 77, 77, 0.04);