docs: Add and document a working Lando setup for local Janeway development

[kopfduenger]

Summary

This PR updates and documents a tested Lando-based local development workflow for Janeway.

What changed

• fix the tracked .lando.yml so a fresh clone has the required shared Lando configuration
• add a dedicated Lando guide under docs/source/dev/lando.rst
• link that guide from the developer installation docs
• remove redundant parallel Lando explanation from docs/source/dev/installation.rst
• link the Lando guide from README.md
• switch local Lando development defaults in src/core/dev_settings.py to:
  • DEFAULT_HOST = "http://janeway.lndo.site"
  • URL_CONFIG = "domain"
• revise the new and touched docs toward plainer, more direct wording by removing “just/simple”-style phrasing where it was avoidable

Why

The previous Lando guidance was outdated for the current repository state. This PR documents a tested workflow and covers practical issues contributors may hit, including:

• current proxy/domain-mode behavior
• startup noise on first boot
• Docker/Lando version expectations
• arm64 vs amd64 package differences
• hosts file fallback when *.lndo.site does not resolve
• post-install domain alignment when installer defaults save localhost

It also reduces duplication in the developer docs by making the dedicated Lando page the main source of truth for this workflow.

Notes for reviewers

• .lando.local.yml remains intentionally local and untracked
• local editable dependency checkouts under src/ are not part of this PR
• the new Lando guide is integrated into the existing Sphinx / Read the Docs structure
• the wording changes aim to keep the setup instructions direct and easier to follow for new contributors