test: split oversized test modules

[adrunkhuman]

Summary

• split oversized database tests into focused contract files under tests/database
• split admin fixture workflow tests into focused admin_panel modules
• split user command tests by command surface
• trim brittle incidental UI/mock assertions while keeping behavior contracts

Verification

• uv run pytest
• uv run ruff check .
• uv run ruff format --check .
• uv run ty check typer_bot

Closes #234