feat: Add auto-trigger for LLM analysis

Introduces a new module `auto_trigger` responsible for opportunistically
initiating LLM analysis jobs. This mechanism scans case directories for
new or updated recordings and transcripts, automatically creating and
queuing analysis jobs when appropriate.

Key components:
- `evaluate_case`: Pure function to determine if a case is ready for
  analysis based on recording status, transcriptions, document
  modification times, and existing job/failure markers.
- `try_enqueue`: Orchestrates the analysis job creation and queuing
  process if `evaluate_case` returns `AutoDecision::Enqueue`.
- `try_enqueue_all_for_user`: Iterates through all user cases to trigger
  `try_enqueue` for eligible ones.
- `write_failure_marker`/`remove_failure_marker`: Handles persistent
  recording of analysis failures and their cleanup.

This feature aims to reduce manual intervention by automatically
analyzing new or changed case data.

server/src/routes/mod.rs

@@ -1,5 +1,5 @@
 mod bulk;
-mod case_actions;
+pub(crate) mod case_actions;
 mod debug;
 mod events;
 mod health;