Add LinkedIn carousel PDF for dCDH estimator announcement

9-slide carousel (slate+teal palette) covering: hook, problem statement
with treatment timeline visual, real-world scenarios, DID_M method,
feature grid, dynamic event study plot, code example, R validation
parity, and CTA. Marketing campaign hero example threads through.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: igerber