Kick off (#1)

* Kick off
* Update LICENSE copyright

migrations/0002_aggregation.sql

@@ -0,0 +1,14 @@
+-- Hourly aggregated check results for data retention
+CREATE TABLE check_results_hourly (
+  id INTEGER PRIMARY KEY AUTOINCREMENT,
+  monitor_name TEXT NOT NULL,
+  hour_timestamp INTEGER NOT NULL,
+  total_checks INTEGER NOT NULL,
+  successful_checks INTEGER NOT NULL,
+  failed_checks INTEGER NOT NULL,
+  avg_response_time_ms INTEGER,
+  min_response_time_ms INTEGER,
+  max_response_time_ms INTEGER
+);
+
+CREATE UNIQUE INDEX idx_hourly_monitor_hour ON check_results_hourly(monitor_name, hour_timestamp);