Cleanup: over-engineering pass

- merge /api/uptime + /api/version into /api/health and /api/stats
- collapse RTMP per-codec dispatch into a single CodecParser path
- dedupe STUN attribute walking (ufrag_pair / parse_xor_mapped_address)
- dedupe StreamCodec <-> str0m Codec mapping via StreamCodec::from_str0m
- dedupe bearer token extraction in WHIP handlers
- replace regex charset validation with stdlib checks
- flatten one-field wrappers (WebRtcProxyConfig, HttpServerConfig, ServerInfo)
- remove SessionCookie extractor (only fed debug logs)
- delete dead code: entity ActiveModel helpers, get_stream_session,
  WebrtcProxy::local_addr, _connected flag, commented-out blocks
- drop unused deps: futures, rand, regex, serde_json

crates/entity/src/stream_session.rs

@@ -50,17 +50,6 @@ impl Model {
         .insert(db)
         .await
     }
-    pub async fn get_stream_session(
-        db: &DatabaseConnection,
-        stream_session_id: i32,
-    ) -> Result<Model, DbErr> {
-        Entity::find_by_id(stream_session_id)
-            .one(db)
-            .await?
-            .ok_or(DbErr::RecordNotFound(format!(
-                "stream_session {stream_session_id}"
-            )))
-    }
     pub async fn get_all_active_sessions(db: &DatabaseConnection) -> Result<Vec<Model>, DbErr> {
         Ok(Entity::find()
             .filter(Column::EndedAt.is_null())