[BUG] LoadbalancerUtils NPE on missing remoteAddress/method

- severity: Medium
- files: `shenyu-plugin/shenyu-plugin-base/src/main/java/org/apache/shenyu/plugin/base/utils/LoadbalancerUtils.java:71-72`
- description: `buildLoadBalanceData` does `Objects.requireNonNull(request.getRemoteAddress()).getAddress().getHostAddress()` and `request.getMethod().name()`. `getRemoteAddress()` can be null for synthetic exchanges; `.getAddress()` can be null; `request.getMethod()` can return null in some Spring versions. Called from dubbo proxy/reference-config paths.
- impact: A request without a resolvable remote address NPEs inside the dubbo proxy path → 500.
- suggested_fix: Null-check and fall back to a safe default.
- confidence: Medium
- related_existing: none

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_Identified during the 2026-08-02 deep re-scan; full list in [`docs/scan2-2026-08-02/06-medium-tiers.md`](docs/scan2-2026-08-02/06-medium-tiers.md)._

Start with shenyu-plugin/shenyu-plugin-base/src/main/java/org/apache/shenyu/plugin/base/utils/LoadbalancerUtils.java, especially buildLoadBalanceData around lines 71-72. Trace its use from the dubbo proxy/reference-config paths and verify how synthetic exchanges can omit remoteAddress or method. Done means those inputs no longer cause an NPE and use a safe fallback instead.

Written by the indexing model from the issue text.