fix: standardize Django logging settings

[saurabhhhcodes]

What changed

• Added a centralized Django LOGGING configuration with a console handler and standardized formatter.
• Wired the log level to DJANGO_LOG_LEVEL, defaulting to DEBUG in development and INFO otherwise.
• Added a small settings test to verify the logging config stays normalized.

Why

• The repo had scattered logger setup and no single Django logging policy.
• A shared config makes it easier to keep backend logs consistent across apps and environments.

Validation

• python3 -m py_compile backend/backend/settings.py backend/users/tests.py backend/campaigns/migrations/0010_merge_0009_campaign_cached_counters_0009_campaignlead_bounce_metadata.py
• git diff --check
• python3 backend/manage.py test users.tests -v 1

Closes #395

[coderabbitai]

Important

Review skipped

Draft detected.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 8cef3c7d-5a5c-4ac8-b3e7-fd68bc4fe8ca

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}