docs/tests: fix remaining dead links and add empty-config export test

[oib]

Motivation

• Finish follow-up review items by repairing remaining broken internal docs links and adding a regression test for an empty config export scenario.
• Ensure the config export behavior remains robust for an empty YAML file by adding a test that captures the expected output.
• Remove the now-obsolete proposal document once fixes are applied in-code.

Description

• Updated docs/8_development/1_overview.md to replace non-existent internal links with existing targets and corrected the issue tracker URL and several Next Steps/Contributing links.
• Added test_export_empty_yaml to tests/cli/test_config.py to verify that an empty .aitbc.yaml exported with --format json returns an empty JSON object ({}).
• Deleted docs/issues/2026-02-17-codebase-task-vorschlaege.md as the actionable items were implemented.

Testing

• Executed PYTHONPATH=cli pytest -q tests/cli/test_config.py which completed successfully with 31 passed.
• Performed a local markdown link existence check against docs/8_development/1_overview.md which reported no missing local links.
• Verified the repository status and committed the changes as a single change-set containing the doc updates, test addition, and deletion of the obsolete issue file.

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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Default only null YAML to empty config

Using yaml.safe_load(f) or {} coerces any falsy top-level YAML value (for example [], false, 0, or "") into {}. In those inputs, config export now silently changes the data instead of exporting what is actually on disk, and users who re-import the export can overwrite their config shape unintentionally. The empty-file fix should only apply when safe_load returns None.

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[chatgpt-codex-connector]

Keep documented Python minimum aligned with runtime

This change documents the infrastructure runtime as Python 3.8+, but service code uses syntax that is not valid on 3.8 (for example built-in generics like dict[str, ...] in apps/coordinator-api/src/app/routers/admin.py). Operators following this guide can provision an unsupported interpreter and hit syntax errors at startup, so the documented minimum here should match the actual service runtime requirement.

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