deps: switch TLS to rustls, drop libssl from the runtime image

OpenSSL came from two removable defaults: teloxide's `default` feature
(native-tls) and x-media's reqwest default features (default-tls). Switch
both to rustls (webpki-roots) so the binary links no system TLS libs:

- teloxide: default-features=false + rustls + ctrlc_handler (was part of
  the removed default)
- reqwest (x-media): default-features=false + rustls-tls

Verified: openssl-sys/native-tls gone from the tree, cargo check clean,
all 5 live twitter/bsky fetches pass over rustls, full container startup
works. The runtime image now needs no libssl.so.3/libcrypto.so.3 or CA
bundle (ffmpeg only processes local files; all downloads go through
reqwest), saving ~8MB.

crates/x-media/Cargo.toml

@@ -4,7 +4,7 @@ version = "1.1.0"
 edition = "2024"
 
 [dependencies]
-reqwest = { version = "0.12", features = ["json"] }
+reqwest = { version = "0.12", default-features = false, features = ["json", "rustls-tls"] }
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 regex = "1.12"