[BUG] KeyWordMatch builds regex from unescaped user keywords — PatternSyntaxException

- severity: Medium
- files: `shenyu-plugin/shenyu-plugin-logging/shenyu-plugin-logging-desensitize-api/.../matcher/KeyWordMatch.java:36-46`
- description: The constructor iterates over the keyword set and appends each keyword directly into a regex `StringBuilder` without escaping: `sb.append(tempKeyWord)`. If any keyword contains regex metacharacters (`(`, `[`, `.`, `*`, `\`, `+`, `?`, `{`, `|`), `Pattern.compile` throws `PatternSyntaxException`. This propagates from `AbstractLoggingPlugin.doExecute()` line 119.
- impact: A single misconfigured keyword containing regex metacharacters breaks all request handling for every request matching that rule.
- suggested_fix: Use `Pattern.quote(tempKeyWord)` to escape each keyword before appending.
- confidence: High
- 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 in shenyu-plugin/shenyu-plugin-logging/shenyu-plugin-logging-desensitize-api/.../matcher/KeyWordMatch.java:36-46 and inspect how the constructor builds its regex, then trace the failure through AbstractLoggingPlugin.doExecute() at line 119. Verify that keywords containing regex metacharacters are treated literally and no PatternSyntaxException breaks matching.

Written by the indexing model from the issue text.