feat(api, web): enhance agent traffic statistics and update installation scripts

- Improved the collection and reporting of agent traffic statistics, including total packets dropped and accepted, to provide a more comprehensive view of agent performance.
- Updated the `evofw-firewall.sh` script to capture and report traffic statistics before chain recreation, ensuring accurate data retention.
- Enhanced the installation script to support updates on already-installed agents, allowing for script and timer refresh without re-enrollment, while preserving existing credentials.
- Refactored UI components to utilize new traffic statistics, improving clarity and user experience in displaying agent performance metrics.

These changes enhance the overall functionality and usability of the agent management system, providing better insights and easier updates for users.

packages/shared/src/contracts.ts

@@ -56,6 +56,9 @@ export const agentSchema = z.object({
   last_apply_prefix_count: z.number().int().nullable().optional(),
   last_apply_packets_dropped: z.number().int().optional(),
   last_apply_packets_accepted: z.number().int().optional(),
+  /** Cumulative until reset (UI Traffic). */
+  total_packets_dropped: z.number().int().optional(),
+  total_packets_accepted: z.number().int().optional(),
   last_apply_kernel_method: z.string().nullable().optional(),
   client_version: z.string().nullable().optional(),
   settings_json: z.string().optional(),