Adopt the modern-di integration kit

[lesnik512]

Summary

modern-di 2.28.0 shipped modern_di.integrations — framework-agnostic primitives that formalize what this package's FromDI/inject already hand-roll. This swaps the hand-rolled internals for kit calls. No public-API change; zero test-file changes.

Tenth of 13 planned adapter conversions (after starlette 2.2.0, fastapi 2.10.0, litestar 2.13.0, aiohttp 2.2.0, flask 2.1.0, faststream 2.10.0, typer 2.3.0, grpc 2.1.0, celery 2.1.0). Like typer/celery, arq has no connection/context object — its per-job ctx is a bare dict — so this is a Layer-2-only conversion. Unlike celery, arq has no double-wrap guard either: inject isn't swept, and the existing _WRAPPED_MARKER protects a different concern (a second setup_di call), left untouched.

• _FromDI deleted; FromDI = integrations.from_di.
• inject calls integrations.parse_markers directly (_parse_inject_params deleted entirely — its body was an exact duplicate); resolves via integrations.resolve_markers(child, di_params).
• The task-specific mechanism (the *args/**kwargs decoration-time TypeError guard, by-name signature binding, functools.wraps, and the async def wrapper shape) is preserved exactly unchanged.
• Dead imports removed: dataclasses, providers, T_co.
• setup_di and all four lifecycle-hook wrappers are untouched.
• architecture/dependency-injection.md promoted to describe the new internals.
• Bumps the modern-di floor to >=2.28,<3.

Test plan

• just test-ci — 100% line coverage, all 14 tests passing, zero test-file changes
• just lint-ci — ruff, ty, check-planning all clean
• Per-task spec + quality review (4 tasks, all approved)
• Whole-branch review (approved, no findings)