feat(redis): add Redis storage package

[mnbuhl]

Summary

• Adds Atomizer.Redis, a StackExchange.Redis-backed storage package that references only Atomizer.
• Implements Redis-backed jobs, schedules, leases, heartbeat recovery, and monitoring queries used by the dashboard.
• Documents Redis setup and adds a Redis service to compose.

Changes

• Registers UseRedisStorage(...) overloads for DI-provided, connection string, existing multiplexer, and factory-based setup.
• Adds contract, lease, heartbeat recovery, dashboard-facing monitoring, and DI coverage for net8/net10.
• Confirmed package metadata includes only Atomizer and StackExchange.Redis; local checks passed with solution build, Redis net8/net10 tests, package creation, and CSharpier check.

[mnbuhl]

Follow-up pushed in 6d97eb2: added samples/Atomizer.Redis.Example with Redis storage, dashboard mapping, sample job endpoints, launch settings, HTTP examples, and README run instructions.

Verified with:

• dotnet build samples/Atomizer.Redis.Example/Atomizer.Redis.Example.csproj
• dotnet csharpier check .
• dotnet build Atomizer.sln --no-restore
• dotnet test tests/Atomizer.Redis.Tests/Atomizer.Redis.Tests.csproj --framework net8.0 --no-build
• dotnet test tests/Atomizer.Redis.Tests/Atomizer.Redis.Tests.csproj --framework net10.0 --no-build

[github-actions]

Package	Line Rate	Health
Atomizer.EntityFrameworkCore	91%	✔
Atomizer	13%	❌
Atomizer.Redis	86%	✔
Atomizer	16%	❌
Atomizer.Redis	86%	✔
Atomizer	16%	❌
Atomizer	77%	✔
Atomizer	77%	✔
Atomizer	77%	✔
Atomizer.EntityFrameworkCore	91%	✔
Atomizer	13%	❌
Atomizer.EntityFrameworkCore	91%	✔
Atomizer	13%	❌
Summary	55% (10844 / 21023)	➖