Add two optional free-text fields to findings so a reporter can record
what was tested and did not work (counterevidence) and why the
conclusion holds (confidence_rationale).
- db: idempotent ADD COLUMN IF NOT EXISTS, TEXT NOT NULL DEFAULT '',
no CHECK; RecordFindingInput, the INSERT, the shared select list and
all three scan sites carry them.
- agent: report_finding accepts both as optional strings; the worker
and pentest prompts say to fill them when confidence is not high.
- server: FindingDTO (list and detail) carries both, omitted when empty;
existing databases get the two schema properties added to the stored
report_finding row once, without overwriting user edits.
- web: the finding detail page shows each section only when non-empty.
Both fields stay optional: a missing field never refuses a finding.