Surface boot exceptions in logs

[jonatanklosko]

First item from #41.

# Some errors prevent the server from starting, for example
# a missing import in urls.py. The process keeps running, just
# without the server. The LLM can fix the issue, then the watcher
# restarts the server and it works as expected. To enable the LLM
# to fix the issue, we need to surface the startup error in the
# logs. The crash results from an uncaught exception in the Django
# thread, so we patch the global excepthook, so that we write the
# exception to the log file.

[josevalim]

Nice find!