maint, use proper logging

[tphoney]

Note

Low Risk
Mostly replaces ad-hoc stdout printing with structured slog calls and adds request body size limits on web handlers; behavior changes are limited to logging output and rejecting oversized requests.

Overview
Standardizes runtime output across Plex/Amazon/CinemaParadiso clients and the web server by replacing fmt.Print* debugging with structured log/slog logging (including better error/warn/info levels and less sensitive settings logging).

Hardens web endpoints by capping request body sizes via http.MaxBytesReader and tweaks progress-bar polling URLs to use numeric job IDs (with gosec suppressions where appropriate). Also refreshes a couple module versions and simplifies utils tests using reflect.DeepEqual.

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