fix(send): migrate rand usage to the 0.10 API

rand 0.10 renamed the entry points dependabot's version bump alone cannot
follow: `thread_rng()` -> `rng()`, `gen_range()` -> `random_range()` and the
`Rng` trait -> `RngExt`.

The jitter only needs one float, so use the free function
`rand::random_range(0.2..0.8)` and drop the now-unused trait import instead
of importing `RngExt`.

Verified: cargo fmt --check, cargo clippy --workspace --all-targets -- -D
warnings, cargo test --workspace --locked (retry_delay_seconds_bounds keeps
the 0.2..0.8 jitter window).

crates/xmedia-bot/src/send/mod.rs

@@ -17,7 +17,6 @@ use crate::link_cache::{CachedMedia, CachedMediaKind, CachedPost};
 use crate::media_sender::MediaSender;
 use input_media::{build_media_group, input_file_for, item_url};
 use post_send::{cache_animation_send, cache_sent_task};
-use rand::Rng;
 use serde::{Deserialize, Serialize};
 use std::sync::LazyLock;
 use teloxide::prelude::*;
@@ -261,7 +260,7 @@ pub fn photos_first(items: Vec<MediaItemPayload>) -> Vec<MediaItemPayload> {
 
 /// Exponential backoff with jitter, capped at 30s.
 pub fn retry_delay_seconds(attempts: u32) -> f64 {
-    let jitter: f64 = rand::thread_rng().gen_range(0.2..0.8);
+    let jitter: f64 = rand::random_range(0.2..0.8);
     (2f64.powi(attempts as i32) + jitter).min(30.0)
 }