Fast mode and preprocess CLI

[stoutta6]

Adding "fast mode" spectrogram generation, a "preprocess" CLI function to produce batches of compressed spectrograms in parallel, and multiple tweaks and fixes to make batbot more error tolerant and handle edge cases.

[bluemellophone]

LGTM, with small cleaning comments.

[codecov]

Codecov Report

❌ Patch coverage is 37.55656% with 276 lines in your changes missing coverage. Please review.
✅ Project coverage is 56.7%. Comparing base (0fdf8b9) to head (3d0f23f).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
batbot/batbot_cli.py	0.0%	196 Missing ⚠️
batbot/spectrogram/__init__.py	78.6%	41 Missing ⚠️
batbot/__init__.py	26.4%	39 Missing ⚠️

❌ Your patch status has failed because the patch coverage (37.5%) is below the target coverage (50.0%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@           Coverage Diff            @@
##            main     #33      +/-   ##
========================================
- Coverage   71.3%   56.7%   -14.6%     
========================================
  Files          6       7       +1     
  Lines        969    1299     +330     
========================================
+ Hits         691     737      +46     
- Misses       278     562     +284     

Files with missing lines	Coverage Δ
tests/test_spectrogram.py	100.0% <100.0%> (ø)
batbot/__init__.py	42.5% <26.4%> (-33.3%)	⬇️
batbot/spectrogram/__init__.py	67.8% <78.6%> (-2.5%)	⬇️
batbot/batbot_cli.py	0.0% <0.0%> (ø)

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 0fdf8b9...3d0f23f. Read the comment docs.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.