Filter topics in topic-list screen

[gnprice]

After #1158, we'll have a screen showing the list of topics in a given channel.

The initial version won't have the "Filter topics" feature, which is shown in the design and is also present in the legacy app. This issue is for adding that feature.

For details, see the design in Figma:
https://www.figma.com/design/1JTNtYo9memgW7vV6d0ygq/Zulip-Mobile?node-id=6819-35869&m=dev

References

• Figma design: https://www.figma.com/design/1JTNtYo9memgW7vV6d0ygq/Zulip-Mobile?node-id=6819-35869&m=dev
• Design thread: #mobile-design > Topic list in channel

[aikansh008]

Hello sir, please assign this isue to me