fix(server): print localhost Swagger URL

[sarvesh1327]

Summary

• Print a browser-usable Swagger UI URL when LitServe binds to wildcard hosts.
• Map 0.0.0.0 and :: to localhost for the user-facing docs link while keeping the actual bind host unchanged.
• Add regression coverage for the display-host helper and the startup message.

Test Plan

• .venv/bin/python -m pytest tests/unit/test_lit_server.py::test_disable_openapi_url_print_message -q (failed before the fix with http://0.0.0.0:8000/docs, passed after)
• .venv/bin/python -m pytest tests/unit/test_lit_server.py::test_display_host_for_url_uses_browser_address tests/unit/test_lit_server.py::test_disable_openapi_url_print_message -q
• uv run --with ruff ruff check src/litserve/server.py tests/unit/test_lit_server.py

Fixes #697