Add Monolog bridge for file-based job execution logging

[yann-eugone]

Summary

• Introduces the yokai/batch-monolog package — a new bridge that writes job execution logs to files using Monolog's StreamHandler, one file per job execution.
• Adds optional subdirectory sharding (configurable depth and segment length) to avoid filesystem performance issues on large workloads.
• Extends the Symfony bundle configuration with a new logging section supporting memory, null, stream (Monolog), and service logger types.
• Documents the new concepts: the job execution logger abstraction, the Monolog bridge, and the Symfony Framework configuration.

New package: yokai/batch-monolog

The bridge exposes two classes:

• StreamJobExecutionLoggerFactory — implements JobExecutionLoggerFactoryInterface. Creates one log file per job execution, named after the job execution id. Supports optional Monolog processors and a custom formatter. Files can optionally be spread across nested subdirectories (similar to how Git stores objects), to keep individual directories manageable at scale.
• StreamJobExecutionLogger — implements JobExecutionLoggerInterface. Wraps a Monolog Logger with a StreamHandler. Reads logs back lazily via getLogs() or as a full string via getLogsContent(). The getReference() value stored with the JobExecution is the path relative to the configured directory, making it portable across environments.

Symfony bundle logging configuration

A new logging key is added to the bundle configuration tree:

yokai_batch:
  logging:
    type: stream          # memory | null | stream | service
    stream:
      directory: '%kernel.logs_dir%/batch'
      sub_directories: 2
      chars_per_directory: 2
      processors: []
      formatter: ~

When type: stream is selected, the bundle wires StreamJobExecutionLoggerFactory automatically.
When type: service, an arbitrary service id can be provided, allowing full customisation.

Documentation

New RST pages:

• core-concepts/job-execution-logger.rst — explains what a job execution logger is, the factory lifecycle (create / restore), and lists all available implementations.
• bridges/monolog.rst — usage examples for the three main scenarios: basic file logging, subdirectory sharding, and custom processors/formatter.

Updated pages:

• bridges/symfony-framework.rst — documents the new logging bundle configuration.
• core-concepts/job-execution.rst — links to the new logger page.
• bridges.rst and index.rst — add the new Monolog bridge to the navigation tree.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.36%. Comparing base (9003a13) to head (954b707).
⚠️ Report is 3 commits behind head on 1.x.

Additional details and impacted files

@@             Coverage Diff              @@
##                1.x     #199      +/-   ##
============================================
+ Coverage     99.32%   99.36%   +0.03%     
- Complexity      994     1054      +60     
============================================
  Files           172      175       +3     
  Lines          3114     3291     +177     
============================================
+ Hits           3093     3270     +177     
  Misses           21       21              

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