Add "around" constraint for fuzzy schedule syntax (#6664)

* Initial plan

* Initial plan for "around" constraint in fuzzy scheduling

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

* Add "around" constraint for fuzzy scheduling

Implement parser support and scattering algorithm for "daily around HH:MM" syntax.
Uses deterministic hash-based scattering within ±2 hour window around target time.

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

* Complete implementation and validation of "around" constraint

All tests pass, code is formatted and linted. Implementation complete.

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

* Add tests and documentation for UTC and am/pm support in "around" constraint

The implementation already supports UTC offsets and am/pm format by reusing the existing parseTime function. Added explicit test coverage and documentation.

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

* Change scattering window from ±2 hours to ±1 hour

Updated window size to 120 minutes (±1 hour) as requested. This provides tighter time constraints while still distributing load.

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

* Add comprehensive fuzz test coverage for "around" constraint

Added seed corpus with valid and invalid "around" schedule patterns including UTC offsets and am/pm formats. Enhanced fuzz test validation to properly handle FUZZY:DAILY_AROUND format.

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>
Co-authored-by: Peli de Halleux <pelikhan@users.noreply.github.com>

Author: Copilot