chore(deps): allow modern-di 4

[lesnik512]

Refs modern-python/modern-di#579.

Summary

• Widen the requirement to modern-di>=3,<5. The lower bound stays, since the integration uses no 4.0-only API.
• Re-checked against modern-di main (f300c2e) and grepped code, tests, README, CONTEXT.md and ADRs for 3.x-only names and behaviour (ContainerClosedWarning, use_lock, the registries, finalizer_errors, optional context, overrides cleared on close). Nothing needed changing. The ContainerClosedError wording in main.py and tests/test_lifespan.py already matches 4.0.
• tests/dependencies.py has message: StreamMessage[typing.Any] | None = None. This is not the 4.0 optional-context change: a parameterized generic is never wired by type, so the default applies on both 3.x and 4.0 and the parameter is always None.

Verification

• 3.x: uv sync resolved modern-di 3.6.0. eof-fixer, ruff format/check and ty pass; pytest 13 passed, coverage 100%.
• 4.0: modern-di main (f300c2e) installed from a local wheel. ty passes; pytest 13 passed, coverage 100%.

This PR stays a draft until modern-di 4.0.0 is on PyPI.