feat: track crawl run employee changes and verify dismissals

migrations/003_crawl_run_employee_changes.sql

@@ -0,0 +1,21 @@
+CREATE TABLE IF NOT EXISTS crawl_run_employee_changes (
+  id SERIAL PRIMARY KEY,
+  crawl_run_id INTEGER NOT NULL REFERENCES crawl_runs(id),
+  employee_id INTEGER REFERENCES employees(id),
+  profile_key VARCHAR(255) NOT NULL,
+  profile_url TEXT NOT NULL,
+  full_name TEXT,
+  change_type VARCHAR(32) NOT NULL,
+  profile_available BOOLEAN,
+  message TEXT,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE INDEX IF NOT EXISTS ix_crawl_run_employee_changes_run_id
+  ON crawl_run_employee_changes (crawl_run_id);
+
+CREATE INDEX IF NOT EXISTS ix_crawl_run_employee_changes_employee_id
+  ON crawl_run_employee_changes (employee_id);
+
+CREATE INDEX IF NOT EXISTS ix_crawl_run_employee_changes_change_type
+  ON crawl_run_employee_changes (change_type);