chore: update all dependencies to latest versions, remove unused serde_json

ratatui 0.21->0.30, crossterm 0.26->0.29, reqwest 0.11->0.13,
open 3.2->5.3, rand 0.8->0.9, tokio 1.0->1.51. Removed serde_json
(only used transitively). Updated APIs for breaking changes: Frame
generics, f.area(), rand::rng(), random_range().

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

Author: program247365