fix: preserve unknown health status in Sentinel updates (PushServerUpdateJob)

## Problem
Services with "running (unknown)" status were periodically changing
to "running (healthy)" every ~30 seconds when Sentinel pushed updates.
This was confusing for users and inconsistent with SSH-based status checks.

## Root Cause
`PushServerUpdateJob::aggregateMultiContainerStatuses()` was missing
logic to track "unknown" health state. It only tracked "unhealthy" and
defaulted everything else to "healthy".

When Sentinel pushed updates with "running (unknown)" containers:
- The job saw `hasRunning = true` and `hasUnhealthy = false`
- It incorrectly returned "running (healthy)" instead of "running (unknown)"

## Solution
Updated `PushServerUpdateJob` to match the logic in `GetContainersStatus`:

1. Added `$hasUnknown` tracking variable
2. Check for "unknown" in status strings (alongside "unhealthy")
3. Implement 3-way priority: unhealthy > unknown > healthy

This ensures consistency between:
- SSH-based updates (`GetContainersStatus`)
- Sentinel-based updates (`PushServerUpdateJob`)
- UI display logic

## Changes
- **app/Jobs/PushServerUpdateJob.php**: Added unknown status tracking
- **tests/Unit/PushServerUpdateJobStatusAggregationTest.php**: New comprehensive tests
- **tests/Unit/ExcludeFromHealthCheckTest.php**: Updated to match current implementation

## Testing
All 31 status-related unit tests passing:
- 18 tests in ContainerHealthStatusTest
- 8 tests in ExcludeFromHealthCheckTest (updated)
- 6 tests in PushServerUpdateJobStatusAggregationTest (new)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

tests/Unit/ExcludeFromHealthCheckTest.php

@@ -19,7 +19,9 @@ it('ensures ComplexStatusCheck returns excluded status when all containers exclu
         ->toContain('// If all containers are excluded, calculate status from excluded containers')
         ->toContain('// but mark it with :excluded to indicate monitoring is disabled')
         ->toContain('if ($relevantContainerCount === 0) {')
-        ->toContain("return 'running:excluded';")
+        ->toContain("return 'running:unhealthy:excluded';")
+        ->toContain("return 'running:unknown:excluded';")
+        ->toContain("return 'running:healthy:excluded';")
         ->toContain("return 'degraded:excluded';")
         ->toContain("return 'exited:excluded';");
 });