feat(reinforce): add traceable reinforce_log to Results

[nader-00]

Description

Results.reinforce_log is a new long-format DataFrame that records why each grid-reinforcement measure happened - the violated component, the exceeded limit, the time step and load/feed-in case - alongside what equipment_changes already tracked (what changed and at what cost), one row per (violation, changed component).

• check_tech_constraints: add a signed max_voltage_dev column, needed to derive issue_type (over-/undervoltage) and the allowed limit.
• reinforce_measures: add optional return_node_mapping to reinforce_lines_voltage_issues/reinforce_mv_lv_station_voltage_issues so voltage-triggered reinforcements can be traced back to the violating node/station.
• reinforce_grid: wire _add_reinforcement_log_entries into every stage that already writes equipment_changes; add a log_reinforcement toggle, a run_id to disambiguate repeated reinforce_grid() calls, human-readable INFO logging per violation, and an end-of-run cost summary grouped by trigger/issue_case/voltage_level.
• Add tests for the signed voltage deviation, cost consistency with grid_expansion_costs, and CSV round-tripping.

Fixes #741

Type of change

• New feature (non-breaking change which adds functionality)

Checklist:

• New and adjusted code is formatted using the pre-commit hooks
• New and adjusted code includes type hinting now
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• The Read the Docs documentation is compiling correctly
• If new packages are needed, I added them the setup.py, and if needed the rtd_requirements.txt, the eDisGo_env.yml and the eDisGo_env_dev.yml.
• I have added new features to the corresponding whatsnew file