feat: add PostgreSQL configuration support for production

[Kishalll]

Pull Request

🔗 Related Issue

Closes #337

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📝 Summary of Changes

Adds PostgreSQL configuration support for production deployments via DATABASE_URL environment variable, while keeping SQLite as the default for local development.

• requirements.txt: Added dj-database-url>=2.2,<3.0 and psycopg2-binary>=2.9,<3.0
• backend/backend/settings.py: Replaced hardcoded SQLite DATABASES dict with dj_database_url.config() that reads DATABASE_URL env var. Falls back to SQLite when not set. Enables SSL when DEBUG=False for production.
• backend/.env.example: Added DATABASE_URL= entry with comments
• README.md: Updated both Stack sections to mention PostgreSQL, added "Production database setup" subsection with connection string example
• Removed previously tracked __pycache__/*.pyc and db.sqlite3 from git index

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🏷️ Type of Change

• 🐛 Bug fix
• ✨ New feature
• ♻️ Refactor
• 📝 Documentation update
• 🎨 UI / Style change
• 🔧 Chore

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🧪 Testing

Steps to test:

1. Run python backend/manage.py check — should report 0 issues
2. Run python backend/manage.py test users leads tenants — all 39 tests pass
3. Without DATABASE_URL set, verify the app uses SQLite (check DATABASES['default']['ENGINE'] is django.db.backends.sqlite3)
4. With DATABASE_URL=postgresql://user:pass@host:5432/db set, verify the app uses PostgreSQL (check DATABASES['default']['ENGINE'] is django.db.backends.postgresql)

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✅ Checklist

• No merge conflicts
• Changes follow the project guidelines
• Documentation updated (if applicable)
• Related issue linked
• Changes tested locally (if applicable)

Summary by CodeRabbit

• New Features
  • Added support for configuring production databases via DATABASE_URL.
  • The app now defaults to SQLite for local development and can use PostgreSQL in production.
• Documentation
  • Updated the README and environment examples with DATABASE_URL placeholders and PostgreSQL connection string guidance.
  • Documented the automatic fallback to SQLite when DATABASE_URL is not provided.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: c234c308-042d-4eea-9399-d72c3780face

📥 Commits

Reviewing files that changed from the base of the PR and between fc0d899 and 894abe5.

📒 Files selected for processing (2)

• backend/config/asgi.py
• backend/config/wsgi.py

✅ Files skipped from review due to trivial changes (1)

• backend/config/asgi.py

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📝 Walkthrough

Walkthrough

The PR adds dj-database-url and psycopg2-binary, switches Django database settings to dj_database_url.config(...) with SQLite fallback, updates ASGI and WSGI settings module defaults, and documents DATABASE_URL usage in .env.example and the README.

Changes

PostgreSQL Production Database Support

Layer / File(s)	Summary
Database config implementation and dependencies requirements.txt, backend/backend/settings.py	Adds dj-database-url>=2.2,<3.0 and psycopg2-binary>=2.9,<3.0 to requirements.txt. Imports dj_database_url in settings.py and replaces the explicit SQLite ENGINE/NAME dict with dj_database_url.config(...), defaulting to sqlite:///BASE_DIR/db.sqlite3, setting conn_max_age=600, and enabling ssl_require when DEBUG is false.
Environment example and README documentation backend/.env.example, README.md	Adds a DATABASE_URL= placeholder and fallback-to-SQLite comments to .env.example. Updates both Stack sections and both backend/.env setup blocks in the README to document DATABASE_URL with a PostgreSQL example connection string.
ASGI and WSGI settings module updates backend/config/asgi.py, backend/config/wsgi.py	Changes the default DJANGO_SETTINGS_MODULE value in both entrypoints from config.settings to backend.settings.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐇 Hoppity-hah, the settings bloom,
DATABASE_URL now lights the room.
SQLite hops for local days,
Postgres prances in prod ways. 🥕

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: adding PostgreSQL production support.
Linked Issues check	✅ Passed	The PR meets the linked issue requirements for DATABASE_URL support, SQLite fallback, env example, README guidance, and psycopg2-binary.
Out of Scope Changes check	✅ Passed	The extra ASGI/WSGI settings module updates are related to the database settings change and do not appear unrelated.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@backend/backend/settings.py`:
- Around line 118-122: The runtime settings are still loading config.settings,
so the database configuration change in backend/settings.py is not being used in
deployment. Update the active settings module backend/config/settings.py to
include the same dj_database_url.config(...) database setup (or, alternatively,
change backend/config/wsgi.py and backend/config/asgi.py to import
backend.settings) so the deployed entrypoints and settings source stay aligned.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: f4baa4a7-9174-494f-b7f6-3b0108f77afe

📥 Commits

Reviewing files that changed from the base of the PR and between 4a33158 and fc0d899.

⛔ Files ignored due to path filters (51)

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📒 Files selected for processing (5)

• README.md
• backend/.env.example
• backend/backend/settings.py
• backend/db.sqlite3
• requirements.txt

[Kishalll]

@Kuldeeep18 pls review