Apply ruff lint fixes across codebase

[rajeee]

Summary

This PR builds on top of PR #207 (ruff formatting) to also apply all ruff lint fixes to the codebase.

• Remove unused imports (F401) in scripts and modules
• Add __all__ lists to __init__.py files to document public API and fix re-export warnings
• Replace star import in test_equipment.py with explicit imports (fixes F403/F405)
• Fix bare except clause in docs/source/conf.py (E722 -> except Exception:)
• Remove unused local variables (F841) or add noqa for intentional ones
• Add noqa comments for acceptable lint exceptions (E402, E741, F403)

Lint Status

Before: 107 errors
After: 0 errors (all checks pass!)

Test Status

All 237 tests pass (1 skipped).

How to run

# Check for lint errors (should show 0 errors)
ruff check .

# Auto-fix any future lint issues
ruff check --fix .

Notes

• Some variables like heating_des_init and cooling_des_init in ochre/utils/equipment.py are kept with # noqa: F841 because they're used dynamically by eval() when loading zone temperature files
• The star import from .Equipment import * in ochre/__init__.py is kept for API compatibility with # noqa: F403