[Observability] pr1 — LogSanitizer + OpenTelemetry dependency baseline #5327

Part of #4070 (Modern Observability for Texera).

Goal

Add the log-sanitization primitives and the pinned OpenTelemetry SDK / test dependency baseline that the rest of the observability stack builds on.

Problem

Before any application logs are bridged to an OTel collector, we need a single, tested sanitizer: untrusted log content can leak secrets (bearer tokens, passwords, AWS keys), forge new log lines via CRLF injection, and expose arbitrary MDC fields. There is also no pinned OpenTelemetry dependency baseline yet.

Scope

• LogSanitizer: secret redaction, C0 control-character stripping, body-size cap, and the MDC-key allowlist.
• Pin the OpenTelemetry SDK deps + scalatest in common/config (the baseline the whole stack depends on).
• Default-off — nothing emits telemetry yet.

Branch: obs/pr1/log-sanitizer