Align docs and metadata checks with current py3plex 2.0 reality

[Copilot]

This update resolves drift between documentation and the current code/release metadata. It brings contributor-facing docs, GUI deployment guidance, and version-check tooling back into agreement with the actual project state.

• Release metadata consistency

  • Updated README stats badges to match the canonical values enforced by version consistency checks.

• GUI docs alignment

  • Removed references to non-existent py3plex[gui] / .[gui] extras.
  • Updated GUI setup/deployment docs to reflect the current gui/ Docker Compose workflow and active ports (8080 UI, 5555 Flower).

• Getting-started version messaging

  • Corrected installation guide language from “py3plex 1.x” to “py3plex 2.x” for current-doc guidance.

• Book verification script freshness

  • Updated PDF artifact consistency check from py3plex:1.1.0 to py3plex:2.0.0.

# before
if 'py3plex:1.1.0' in text:
    version_pages.append(page_num + 1)

# after
if 'py3plex:2.0.0' in text:
    version_pages.append(page_num + 1)

[SkBlaz]

@copilot conflicts

[Copilot]

@copilot conflicts

Conflicts are resolved. I merged origin/master into this branch and fixed the README badge conflict in commit 455585b.