v0.3.0

Features

• NewManagerFromFileWithWatch — new constructor that reads ff4go.json and automatically reloads flags when the file changes, without restarting the process. The returned *Manager pointer is updated in place on each change.
• NewManagerFromBytes — new constructor that accepts raw JSON bytes, enabling initialization from embedded files (//go:embed), environment variables, or remote sources.
• IsEnabledForUserAndEnvironment — new method that returns true only when both the user and environment targeting checks pass simultaneously.
• HasFlag — new method that reports whether a flag with the given name exists in the manager.
• endAt rule — new Rules field (RFC 3339 string) that disables a flag after a given timestamp, regardless of other rules. Applies to IsEnabled, IsEnabledForUser, IsEnabledForEnvironment, and IsEnabledForUserAndEnvironment.
• Deterministic percentage rollout — Percentage targeting now uses an FNV-64a hash of "flagName:id" instead of a random value, ensuring the same user always gets the same result for a given flag.

Bug Fixes

• IsEnabled now respects endAt — previously IsEnabled did not check the endAt rule and could return true for expired flags.