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>

db.py

@@ -153,7 +153,7 @@ def set_ticket_id(event_id: int, ticket_id: str) -> None:
             )
 
 
-def get_active_events() -> list:
+def get_active_events(limit: int = 200, offset: int = 0) -> list:
     with get_conn() as conn:
         with conn.cursor() as cur:
             cur.execute(
@@ -161,7 +161,9 @@ def get_active_events() -> list:
                    WHERE resolved_at IS NULL
                    ORDER BY
                      FIELD(severity,'critical','warning','info'),
-                     first_seen DESC"""
+                     first_seen DESC
+                   LIMIT %s OFFSET %s""",
+                (limit, offset),
             )
             rows = cur.fetchall()
             for r in rows:
@@ -171,6 +173,16 @@ def get_active_events() -> list:
             return rows
 
 
+def count_active_events() -> int:
+    """Return count of all unresolved events (for pagination)."""
+    with get_conn() as conn:
+        with conn.cursor() as cur:
+            cur.execute(
+                "SELECT COUNT(*) AS n FROM network_events WHERE resolved_at IS NULL"
+            )
+            return cur.fetchone()['n']
+
+
 def get_recent_resolved(hours: int = 24, limit: int = 50) -> list:
     with get_conn() as conn:
         with conn.cursor() as cur: