fix(config): enable documentation mode only explicitly

ConfigEOS.documentation_mode() was true as soon as Sphinx was imported
anywhere in the process. A test importing Sphinx therefore switched all
later tests into documentation mode, and test_config_md_current failed
depending on test order. Documentation mode is now enabled only by the
documentation generators (_force_documentation_mode) or by the Sphinx
configuration, which sets sys._called_from_sphinx in docs/conf.py.

Declare _force_documentation_mode as a ClassVar. Without the annotation
pydantic turned it into a private attribute, and the class attribute was
a truthy descriptor object.

Behavior change: because of that descriptor, every running EOS was in
documentation mode, so the get_adapter/config/measurement/prediction/ems/
database/resource_registry() guards never raised "access before init" and
created the singletons lazily on first access. They now raise for every
access before initialization. The worker process of uvicorn's auto-reload
(server.reload, make run-dev) relied on that: the app's lifespan now sets up
the configuration and initializes the singletons that do not exist yet.

Leave runtime state out of the documentation: the Home Assistant entity ID
properties and OptimizationCommonSettings.keys return an empty list in
documentation mode, so entity IDs and solution keys of a running system
no longer reach the generated configuration docs.

Keep the tests isolated: test_doc sets documentation mode on the class
and test_docstringrst restores sys._called_from_sphinx after reading the
Sphinx configuration. Add tests for how documentation mode is enabled and
for the runtime values it leaves out.

Additional changes
- Generate openapi.json in documentation mode, as the config docs.
- Share the documentation mode check as coreabc.documentation_mode().
- Move the logging and server address setup of run_eos() to setup_eos_config().
- Test that EOS starts with server.reload.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_doc.py

@@ -9,6 +9,8 @@ from unittest.mock import patch
 
 import pytest
 
+from akkudoktoreos.config.config import ConfigEOS
+
 DIR_PROJECT_ROOT = Path(__file__).parent.parent
 DIR_TESTDATA = Path(__file__).parent / "testdata"
 
@@ -205,10 +207,10 @@ def test_config_md_current(config_eos, set_other_timezone):
 
         # Create test files
         try:
-            config_eos._force_documentation_mode = True
+            ConfigEOS._force_documentation_mode = True
             config_md = generate_config_md.generate_config_md(tested[0], config_eos)
         finally:
-            config_eos._force_documentation_mode = False
+            ConfigEOS._force_documentation_mode = False
 
     # Check test files are the same as the expected files
     for i, expected_path in enumerate(expected):