Apply ruff formatting across the codebase (baseline cleanup)

[abhishek-8081]

The ruff linter was added across the development-* branches (ruff.toml, CI lint workflow),
but the existing code was never reformatted to match ruff's style. ruff format --check .
currently reports 32 files in app/ and tests/ that would be reformatted.

This affects the shared codebase, so the same files are unformatted on every branch that
predates the linter — development, development-approach-b, development-approach-c, etc. It's
not specific to any one approach.

It isn't blocking anything right now — CI only runs ruff check app/ (which passes), the
lint job is continue-on-error, and ruff format --check isn't run in CI. But the baseline
should be cleaned up so the codebase is consistently formatted.

Open question

Where should the reformat run? Since it's shared code, doing it once on development (or
wherever the branches converge) and letting it propagate is cleaner than reformatting each
approach branch separately — otherwise we get conflicting formatting changes across
branches.

Scope

• Run ruff format . across the repo — formatting only, no logic changes.
• Confirm ruff format --check . reports 0 files afterward.
• Confirm ruff check . and the full test suite still pass.

When

Do this at the end / at merge time , after in-flight feature work is merged, so a
repo-wide reformat doesn't collide with open feature PRs.

Acceptance criteria

• ruff format --check . passes (0 files).
• ruff check . passes.
• Full test suite passes.
• Diff is formatting only, no logic changes.