feat: live tracker suite - WIKITOOL_TASKS_CONFIG override, real-tracker tests for Super Productivity and CalDAV, nightly workflow and test image (#156)

Files changed:
- .gitea/scripts/start-radicale.sh
- .gitea/sp-live/Dockerfile
- .gitea/sp-live/resolve-version.sh
- .gitea/workflows/ci.yml
- .gitea/workflows/sp-live-image.yml
- .gitea/workflows/tracker-live.yml
- .gitignore
- CHANGES.md
- DEVELOPMENT.md
- INSTALL.md
- VERSION
- instructions/dev/doc-pull-through.md
- instructions/dev/stack-dev/SKILL.md
- instructions/dev/testing-conventions.md
- instructions/dev/tracker-testing.md
- kb/gtd/INDEX.md
- kb/gtd/technik/Chemenu 8.0.0 freigeben.md
- kb/gtd/technik/Windows nativ unterstützen.md
- kb/index.md
- tools/CONTRACT.md
- tools/chemenu/commands/docs_verify.py
- tools/chemenu/commands/doctor.py
- tools/chemenu/commands/review_cmd.py
- tools/chemenu/commands/task_cmd.py
- tools/chemenu/config.py
- tools/chemenu/tasks/config.py
- tools/chemenu/tests/conftest.py
- tools/chemenu/tests/fixtures/sp/MANIFEST.json
- tools/chemenu/tests/fixtures/sp/api/health.json
- tools/chemenu/tests/fixtures/sp/api/projects.json
- tools/chemenu/tests/fixtures/sp/api/tags.json
- tools/chemenu/tests/fixtures/sp/api/tasks.json
- tools/chemenu/tests/fixtures/sp/seed-backup.json
- tools/chemenu/tests/record_sp_fixtures.py
- tools/chemenu/tests/sp_headless.py
- tools/chemenu/tests/test_doctor.py
- tools/chemenu/tests/test_review.py
- tools/chemenu/tests/test_sp_recorded.py
- tools/chemenu/tests/test_task_cmd.py
- tools/chemenu/tests/test_tasks_config.py
- tools/chemenu/tests/test_tracker_live.py
- tools/chemenu/tests/tracker_live.py
- tools/pytest.ini

instructions/dev/testing-conventions.md

@@ -130,7 +130,7 @@ Whenever you add or change a test under `tools/chemenu/tests/`.
    fixture creates that machine.
 
 4. **Adding a new environment variable to the tool?** Add it to `_WIKITOOL_ENV` in
-   `conftest.py` in the same change. A variable the tool reads and the fixture does not clear
+   `conftest.py` in the same change (`WIKITOOL_TASKS_CONFIG` is one). A variable the tool reads and the fixture does not clear
    is the exact hole this whole file is about, reopened.
 
 5. **Writing a fixture that builds a tree?** Repoint `config.ROOT` at it and call
@@ -168,6 +168,10 @@ Whenever you add or change a test under `tools/chemenu/tests/`.
 - **A test genuinely needs the developer's real environment?** There is no such test, and a new
   one is a design problem rather than an exception: what it wants is a fixture that *builds*
   the state it needs inside `tmp_path`. Building it is also the only version CI can run.
+  The one deliberate exception is the `live_tracker` suite, which talks to a real tracker and
+  may start a real application; it is opt-in through `CHEMENU_LIVE_*` variables, skips without
+  them, and the default run needs neither network nor tracker. Its rules:
+  [tracker-testing.md](tracker-testing.md).
 - **A test patches `config.default_author` directly** (as
   `test_new_source_fails_hard_without_any_author` does)? Keep the patch. It is not made
   redundant by the fixture - it pins the value under test regardless of what the environment