Add waste audit and improvement plan

[dendencat]

Motivation

• Capture and communicate areas of unnecessary complexity and maintenance cost found in the repository (duplicated Django app layout, multiple Docker/Nginx artifacts, debug artifacts, prod-time makemigrations, dependency sprawl, CSRF/test divergence, duplicated static assets, and potential N+1 query issues).
• Provide maintainers with a prioritized, low-risk path to reduce cognitive load, security risk, and CI/deploy instability.
• Create a single reference document to coordinate follow-up cleanup PRs and CI changes.

Description

• Add docs/waste-audit-improvement-plan.md which contains a detailed audit of wasteful or risky files/configs, per-item risk analysis, and concrete remediation guidance.
• The document classifies targets into immediate deletion, consolidation, and design-review buckets and includes a phased roadmap (Phase 0–4), recommended tasks and success metrics.
• No application code or runtime configuration was changed in this PR; only the new documentation file was added.

Testing

• Run git diff --check which reported no issues.
• Executed python -m pytest -q after creating a local logs/ directory to satisfy the project's logging handler; the test run executed 16 tests with 10 passing and 6 failing.
• The observed test failures are caused by environment/repository issues unrelated to this documentation addition (Redis hostname resolution preventing cache-backed sessions and a missing markdown linkify extension causing a markdown rendering test to fail), and should be resolved before larger cleanup that affects runtime behavior.

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Codex Task