feat: Events command implementation

Summary

Add CLI support for the backend event subsystem so users can manage and resolve runtime events directly from the CLI.

This feature brings parity with the backend event APIs by exposing commands for CRUD operations and runtime event resolution through the CLI interface.

The implementation should support the same behavior and validation semantics currently available in the backend service.

Background

The backend already exposes event management and runtime event resolution through /api/v1/events endpoints.

Currently, interacting with these endpoints requires direct API usage. This issue tracks adding equivalent functionality to the CLI to improve developer workflows, operational tooling, debugging, and scripting support.

Expected Behavior

Users can manage events directly from the CLI
CLI requests map to the existing backend event APIs
Runtime event resolution supports page-context lookups
Filter payloads are serialized correctly before submission
Backend validation and conflict behavior are surfaced clearly in CLI responses

Acceptance Criteria

CLI supports all existing event CRUD endpoints
CLI supports resolving the current active event by page route
X-Page-Route behavior is correctly implemented for runtime event resolution
Event filter payloads support:
- enums
- UUIDs
- date values
- nested filter structures
CLI properly handles:
- empty responses
- invalid IDs
- malformed payloads
- duplicate active event conflicts (409)
Help text and command documentation are added
Tests are added for:
- CRUD operations
- current event resolution
- serialization behavior
- conflict/error handling

Notes

Runtime event resolution should mirror backend behavior exactly
If no matching active event exists, the CLI should return an empty/null response
If multiple active events match the same page context, backend conflict responses should be surfaced without modification
Event scheduling behavior remains fully backend-driven via start_date and end_date