[FEATURE] client-side search for e2ee rooms

[luphoria]

Describe the problem

Because end-to-end-encrypted rooms do not support message content searching, a client-side search alternative for these rooms would be very appreciated.

Describe the solution you'd like

I would like to be able to search for messages in encrypted rooms, and this would be a solution which appears the same (maybe with different subtext), and has the same function, but is done using a client-side search.

Alternatives considered

No response

Additional context

See #763

[s41uc0]

+1, this would be a nice addition to keep security a basic, not a compromise :)

[cyrneko]

I generally dislike bumping issues, however since this issue was created Cinny has gotten quite a revamp overall, but also in the search department

it would be really nice to be able to use Cinny to search through encrypted messages, especially account-wide.