💡 Add riscv64 to binary releases

**Describe the feature you'd like**
Id like to have cloudflared compiled as a binary I can install for debian 13, since I run a riscv64 system, not having to compile every release would be somewhat convient

**Describe alternatives you've considered**
manual compiling program and systemd daemon I wrote

**Additional context**
nothing much, other than perhaps adding riscv64 would be wise as maybe more riscv64 based servers might exiest in the future idk

Start by locating the binary release configuration and its supported architecture matrix, then trace how Debian packages are produced. Add riscv64 support where the release process defines architectures and verify that a cloudflared binary is published for Debian 13 riscv64 without requiring manual compilation.

Written by the indexing model from the issue text.