Update dataset card and disclosure to v0.5

v0.4 source ledger: disclosure at first exposure, Layer 3 wording

v0.4: AI-assistance disclosure at first exposure (EU AI Act Art 50(4) wording); Zenodo 21848133

v0.3: bundle alignment, narrowed COI guarantee, Layer 3 sensitivity

v0.2: FY2025 re-base (Layer 1b), Douglas County potable/reclaimed split, Wisconsin re-tagged planning_not_measured

ai-water-tracker dataset: data + reproducer + card

initial commit