fix: replace broad except Exception with specific error handling

[themavik]

Summary

Fixes #11

Every router endpoint catches Exception and returns HTTP 400, masking actual server errors (TypeError, AttributeError, etc.) as "bad request" responses and swallowing tracebacks.

Root Cause

The pattern used across all five router modules:

except Exception as e:
    raise HTTPException(status_code=400, detail=f"Failed to ...: {str(e)}") from e

This conflates client input errors with server-side bugs. A TypeError from a code defect is reported as a 400 instead of a 500, and the original traceback is lost from the client's perspective.

Changes

Across batch.py, configs.py, platforms.py, remediation.py, and reports.py:

1. Narrowed exception handlers from except Exception to except (ValueError, KeyError) — these are the expected input-validation failures (invalid platform names, missing fields, unsupported formats) that warrant a 400 response.

2. Removed try/except entirely from endpoints that access known-good stored data and have no expected failure mode (get_batch_job_status, get_report_summary, list_platforms). These already validate inputs before the service call (e.g. 404 for missing jobs).

3. Unexpected exceptions propagate to FastAPI's default 500 handler, which preserves the full traceback in server logs for debugging.

Testing

• Client input errors (invalid platform, bad config text) still return 400 with descriptive messages
• Unexpected server errors now correctly return 500 and log the full traceback
• 404 paths (missing jobs, reports, remediations) are unchanged