feat(worker): add cron scheduling and durable Redis coordination

[hyp3rd]

• Add cron task registration APIs (standard + durable) with validation and logging
• Wire cron lifecycle into TaskManager; default cron location to UTC and add WithCronLocation
• Add Redis durable coordination: global rate limiting + leader lock using Lua scripts/keys
• Add unit + integration coverage for cron tasks and Redis coordination
• Add robfig/cron/v3 dependency

[Copilot]

Pull request overview

This PR adds cron-based task scheduling and Redis-based coordination features (global rate limiting and leader election) to the worker library.

Changes:

• Adds cron task scheduling with support for both in-memory and durable tasks using robfig/cron/v3
• Implements Redis-based global rate limiting using token bucket algorithm via Lua script
• Implements Redis-based leader lock for single-leader coordination across distributed workers
• Adds workerctl durable enqueue command for creating durable tasks from JSON/YAML/base64 payloads

Reviewed changes

Copilot reviewed 18 out of 19 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
cron.go	New file implementing cron task registration, scheduling, and lifecycle management with 5-field and 6-field schedule support
worker.go	Integrates cron scheduler lifecycle (init, start, stop) into TaskManager
options.go	Adds WithCronLocation option for configuring cron timezone (defaults to UTC)
durable_redis.go	Adds global rate limiting and leader lock coordination features with Lua scripts for atomic operations
tests/cron_test.go	Unit tests for standard and durable cron tasks
tests/durable_redis_integration_test.go	Integration tests for global rate limit and leader lock features
cmd/workerctl/durable_enqueue.go	New command for enqueueing durable tasks with JSON/YAML/base64 payload support
cmd/workerctl/durable_enqueue_test.go	Unit tests for enqueue command payload handling
cmd/workerctl/durable_enqueue_integration_test.go	Integration test for enqueue command
cmd/workerctl/durable_snapshot.go	Adds buffer size configuration for handling large snapshot lines and fixes file path handling
cmd/workerctl/durable_delete.go	Improves delete target labels to show source queue information
cmd/workerctl/durable.go	Registers new enqueue subcommand
pkg/worker/v1/*.pb.go	Removes trailing blank lines (formatting)
go.mod, go.sum	Adds robfig/cron/v3 dependency and promotes gopkg.in/yaml.v3 from indirect to direct
cspell.json	Adds "PEXPIRE" and "robfig" to spell check dictionary
README.md	Documents cron scheduling, Redis coordination features, and enqueue command usage

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[Copilot]

The location parameter in cronParserStandard and cronParserSeconds is unused. While cron parsers can be configured with a location, the robfig/cron/v3 library uses the location at the cron instance level (set via WithLocation in initCron), not at the parser level. These parameters should be removed since they're not used.