Events: add AWS Community Day Shenzhen to the community calendar (#891)

The 3D cloud-native topology session was accepted by 2026 亚马逊云科技
Community Day · 深圳 (Oct 17), a week before the Hong Kong edition
(Oct 24). Same talk, delivered in Chinese rather than English.

Adds an optional `lang` field so one session appearing at two events in
different languages is distinguishable, rendered as a small chip next to
the speaker. Only shown where a talk sets it, so every existing entry is
unaffected.

The Shenzhen agenda is not published yet, so the title carries the
English one the session is already listed under, with a note in the data
file to swap in the Chinese title once the agenda lands.