fix(Local Evaluation): Omit segments from environment flags evaluation

[emyller]

Environment flags return only environment defaults, excluding segment-based targeting.

See Flagsmith/flagsmith#6051.

Changes

• Modify getEnvironmentFlagsFromLocalEvaluationContext() to omit segments from evaluation context
• Add test verifying environment flags ignore segments while identity flags respect them
• Add test fixture with segment matching environment-level context

Closes #116

Review effort: 1/5