Add calibrated DP noise

confium privacy dp --value 1337.0 --sensitivity 1.0 --epsilon 0.5
confium privacy dp --value 88.1 --sensitivity 10 --epsilon 0.1 \
  --distribution gaussian --delta 0.00001

• Laplace is the default and needs only epsilon; Gaussian adds delta and suits higher-sensitivity queries.
• Log (value, sensitivity, epsilon, delta) with every release — the privacy budget composes across releases and auditors will ask.