feat(POP-3811): support World ID bedrock user agents

[Guardiola31337]

Description

• Follow-up to https://github.com/worldcoin/oxide/pull/1050 and [POP-3811] support World ID walletkit user agents walletkit#416.
• Add Bedrock User-Agent helpers so World App clients keep WorldApp headers while World ID clients can send WorldID headers.

Changes

• Add UniFFI-exported UserAgent and UserAgentBuilder primitives.
• Map android-id / ios-id client names to WorldID; keep all other client names on WorldApp.
• Add helpers for app, Bedrock, and client suffix segments.
• Re-export the new primitives from bedrock.

Testing Instructions

• cargo fmt --check
• cargo test -p bedrock user_agent --lib
• cargo clippy --all-targets --all-features -- -D warnings
• ./kotlin/build_kotlin.sh
• ./build_android_local.sh 0.2.14-SNAPSHOT
• Attempted cargo test -p bedrock --lib; the ERC4626 tests require local anvil, which is not installed in this environment. Non-anvil tests passed before that blocker.