Add RISC-V 64-bit (riscv64) platform support

[gounthar]

Both Temurin and Liberica already publish riscv64 JDK builds (confirmed via Adoptium API and Bellsoft API respectively), but the disco-integration bridge does not recognize riscv64 as a platform, so these builds cannot reach SDKMAN's version database.

Changes needed

1. Platform.java: add LINUX_RISCV64 enum value
2. Release.java: map ("linux", "riscv64") to Platform.LINUX_RISCV64
3. Broker.java: map ("linux", "riscv64") to "linuxriscv64"
4. application.properties: add riscv64 architecture entries for vendors that ship riscv64 JDKs (Temurin, Liberica)

Evidence

Adoptium (Temurin) ships riscv64 JDKs (21, 22, 23, 24, 25):

https://api.adoptium.net/v3/info/release_names?architecture=riscv64&image_type=jdk&os=linux&release_type=ga&project=jdk

Bellsoft (Liberica) ships riscv64 JDKs (17 through 25):

https://api.bell-sw.com/v1/liberica/releases?os=linux&arch=riscv&bitness=64&package-type=tar.gz&bundle-type=jdk

The Disco API already serves riscv64 packages (confirmed by the Disco API maintainer and verified via curl):

https://api.foojay.io/disco/v3.0/packages?distribution=temurin&latest=available&release_status=ga&architecture=riscv64&operating_system=linux&package_type=jdk&archive_type=tar.gz

The missing piece is the disco-integration bridge, which does not yet map riscv64 as a recognized architecture.

Related

• feat: add RISC-V 64-bit platform support sdkman-cli#1496: adds riscv64 platform detection to the shell CLI
• feat: add RISC-V 64-bit platform support sdkman-cli-native#375: adds riscv64 to the native CLI release pipeline

This issue tracks the missing middle piece: source (Disco API) → bridge (disco-integration) → database → CLI.