feat: scrub sensitive data from OpenTelemetry traces [OTEL-014]

[damacus]

Summary

Implements sensitive data scrubbing for OpenTelemetry traces to prevent PII leakage in observability data.

Closes Beads issue: med-tracker-ry5

Changes

New Files

• lib/otel/span_sanitizer.rb — Core sanitizer that redacts PII patterns (emails, dates, IPs) from string values and identifies sensitive attribute keys
• lib/otel/span_sanitizing_processor.rb — OpenTelemetry SpanProcessor that applies sanitization on span start

Modified Files

• config/initializers/opentelemetry.rb — Changed PG db_statement from :include to :obfuscate, registered SpanSanitizingProcessor

Test Files

• 34 new tests across 3 spec files covering sanitizer, processor, and integration

Sensitive Data Protection

Vector	Before	After
SQL statements	Raw SQL with PII	Obfuscated
PII attribute keys	Passed through	[REDACTED]
Email patterns	Passed through	[EMAIL REDACTED]
Date patterns	Passed through	[DATE REDACTED]
IP addresses	Passed through	[IP REDACTED]
Auth/cookie headers	Passed through	[REDACTED]