Add secure structured API logging

[Alidantech]

Summary

• replace sentence-based logs with compact typed REQ/RES/ERR/RETRY/CACHE/AUTH events
• add production-safe global levels and immutable client-only per-call logging options
• centralize bounded mandatory redaction before default or custom logger sinks
• log each operation once with concise retries, total duration, and network/cache source
• document configuration, debugging, migration, redaction, and custom sinks

Public API

• ApiLoggingLevel: none, errors, basic, detailed
• ApiCallLogOptions through ApiRequestOptions.log
• typed request/response/error/retry/cache/auth event subclasses
• ApiLogFormatter and CallbackApiLogger

Existing ApiLogger, ApiLogEvent, ApiLogLevel, ApiLoggingConfig.enabled, and legacy metadata booleans remain supported.

Security

Mandatory redaction covers credentials, tokens, authorization, cookies, secrets, API keys, OTP/PIN values, signed URL parameters, nested structures, long values, cycles, binary data, streams, and multipart uploads. Logger failures cannot affect requests or authentication transitions.

Validation

• dart format --output=none --set-exit-if-changed .
• flutter analyze
• flutter test (36 passed)
• flutter analyze in example
• dart pub publish --dry-run (0 warnings)

Generator boundary

Runtime forwarding support is complete. Direct log: parameters on generated operations require the external generator/templates intentionally absent from this repository and remain tracked in #15.

Closes #14
Closes #16
Refs #15