Add pagination to event queries, input validation, daily event purge

- get_active_events() now takes limit/offset (default 200) to cap unbounded queries
- count_active_events() added to return total for pagination display
- /api/events supports ?limit=, ?offset=, ?status= query params (max 1000)
- /api/status includes total_active count alongside paginated events list
- index() route passes total_active to template for server-side truncation notice
- Show "Showing X of Y" notice in dashboard when events are truncated
- Suppression POST validates: reason ≤500 chars, target_name/detail ≤255 chars
- _purge_old_jobs_loop runs purge_old_resolved_events(90d) once per day

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

static/style.css

@@ -2201,3 +2201,17 @@ a:hover { text-decoration: underline; text-shadow: var(--glow-amber); }
   padding: 2px 7px;
   border-radius: 10px;
 }
+
+/* ── Pagination notice ────────────────────────────────────────────── */
+.pagination-notice {
+  font-size: .8em;
+  color: var(--text-muted);
+  padding: 6px 0 8px;
+}
+.pagination-notice a {
+  color: var(--accent);
+  text-decoration: none;
+}
+.pagination-notice a:hover {
+  text-decoration: underline;
+}