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_key.rs

@@ -91,27 +91,3 @@ impl Entity {
             .await
     }
 }
-
-impl ActiveModel {
-    pub async fn change_label_value(
-        mut self,
-        db: &DatabaseConnection,
-        value: String,
-    ) -> Result<Model, DbErr> {
-        self.label = Set(value);
-        self.update(db).await
-    }
-
-    pub async fn password(
-        mut self,
-        db: &DatabaseConnection,
-        value: String,
-    ) -> Result<Model, DbErr> {
-        self.password = if value.is_empty() {
-            Set(None)
-        } else {
-            Set(Some(value))
-        };
-        self.update(db).await
-    }
-}