Minimize cross-package dependencies in component packages

[Alek99]

Summary

• Move the connection banner implementation into the main reflex package so reflex-components-core no longer depends on Lucide or Sonner for that module.
• Remove Sonner's Lucide dependency by typing loading_icon as a generic Component.
• Keep upload rejection toasts working from reflex-components-core via the existing toast ref instead of importing Sonner directly.
• Add regression tests that assert the intended package boundaries stay clean.

Connection Banner Visual Check

The connection banner should look the same as before. I tested origin/main and this PR branch with the same fixture, viewport, light page background, and forced websocket disconnect. The only expected text difference is the dynamic local websocket port.

I also compared the rendered output for ConnectionBanner, ConnectionModal, and ConnectionPulser against origin/main; all matched.

Validation

• uv run ruff format --check reflex/components/banner.py reflex/app.py reflex/utils/codespaces.py packages/reflex-components-core/src/reflex_components_core/core/__init__.py packages/reflex-components-core/src/reflex_components_core/core/upload.py packages/reflex-components-sonner/src/reflex_components_sonner/toast.py tests/units/components/core/test_banner.py tests/units/components/test_package_dependencies.py
• uv run ruff check reflex/components/banner.py reflex/app.py reflex/utils/codespaces.py packages/reflex-components-core/src/reflex_components_core/core/__init__.py packages/reflex-components-core/src/reflex_components_core/core/upload.py packages/reflex-components-sonner/src/reflex_components_sonner/toast.py tests/units/components/core/test_banner.py tests/units/components/test_package_dependencies.py
• uv run pytest tests/units/components/core/test_banner.py tests/units/components/core/test_upload.py tests/units/components/test_package_dependencies.py
• uv run pyright packages/reflex-components-sonner/src/reflex_components_sonner/toast.py packages/reflex-components-core/src/reflex_components_core/core/upload.py reflex/components/banner.py
• Render output comparison against origin/main for ConnectionBanner, ConnectionModal, and ConnectionPulser
• Browser screenshot comparison against origin/main with the same forced-disconnect fixture

Fixes #6324

[codspeed-hq]

Merging this PR will not alter performance

✅ 24 untouched benchmarks

---

_{Comparing codex/issue-6324-package-deps (764e9fa) with main (9ed3692)}