New LLM feature: Starred events to forensic report (stored as a Story)

[itsmvd]

This PR adds a new LLM-powered feature to automatically generate forensic reports (stored as a Story) from starred events.

• Adds a "Generate forensic report" button that appears when starred events filter is active
• Processes starred events through an LLM provider to create a forensic analysis report
• Stores the generated report as a Story
• Implements metrics for tracking events processed and stories created
• Limits initial implementation to 1000 starred events per report (will be expanded once we add max_token_count tracking for LLM providers)

New button in EventList.vue (only visible when viewing starred events)

Example LLM generated report from starred events

[itsmvd]

Two notes:

• Will add tests after first review is done
• _run_timesketch_query will be abstracted to a helper function in a next PR, as we refactor it to use streaming instead
• This first version does not yet take tags and comments of events into account, will add that in a next PR (Include "tags" and "comments" to the llm_forensic_report feature #3333)

[jaegeral]

comment from the sideline, I believe keeping the limit to 1000 events is plenty, even if we increase the possible number to use for llm in general, having somewhat of a limit here could be just fine.