Make root log level configurable via LOG_LEVEL in config

[t0kubetsu]

Summary

Fixes #101

The root logger was hardcoded to DEBUG unconditionally at startup. Production deployments had no way to reduce log noise without patching source code. Debug output can also inadvertently log sensitive request payloads.

Changes

webapp/app/__init__.py

• Move basicConfig after app.config.from_object("config") so LOG_LEVEL is available from config
• Read the level name from app.config.get("LOG_LEVEL", "WARNING") with a safe fallback

webapp/config.py.template

• Add LOG_LEVEL = "WARNING" with a comment explaining the valid values

# Before — hardcoded DEBUG always
logging.getLogger().setLevel(logging.DEBUG)

# After — driven by config, defaults to WARNING
_log_level_name = str(app.config.get("LOG_LEVEL", "WARNING")).upper()
_log_level = getattr(logging, _log_level_name, logging.WARNING)
logging.getLogger().setLevel(_log_level)

Test plan

• Start app with default config.py.template — verify only WARNING+ messages appear in logs
• Set LOG_LEVEL = "DEBUG" in config and restart — verify DEBUG messages appear
• Set LOG_LEVEL = "INVALID" — verify app falls back to WARNING without crashing