Fix critical memory leaks causing production downtime in aspireappacaapiservice-2

[Copilot]

This PR addresses critical memory leaks that caused production downtime with 97% memory utilization and ~1.07 GB of System.Byte[] allocations in the aspireappacaapiservice-2 container app.

Root Cause Analysis

The incident was caused by multiple memory leaks in the application:

1. Static List<byte[]> memoryHog - The /api/app/crash endpoint accumulated 10MB byte arrays in a static list that never got garbage collected
2. Static Processor cache - The /api/app/memleak endpoint accumulated Customer objects indefinitely without cleanup
3. Publisher-Subscriber leak - 2,100 subscribers each holding 1MB of data were created at startup and never unsubscribed, preventing garbage collection
4. Startup memory pressure - Subscriber.CreatePublishers() was called automatically during application startup

Changes Made

1. Fixed Static Memory Hog (AppController.cs)

- private static readonly List<byte[]> memoryHog = new();
+ // Use local variable instead of static to allow garbage collection
+ var localMemoryHog = new List<byte[]>();

2. Added Cache Cleanup (AppController.cs)

+ public void ClearCache()
+ {
+     cache.Clear();
+ }

+ // Clear the cache to prevent memory accumulation
+ p.ClearCache();

3. Fixed Publisher-Subscriber Memory Leak (PublisherSubscriber.cs)

• Added IDisposable pattern with proper unsubscribe mechanism
• Modified CreatePublishers() to clean up subscribers after creation
• Fixed nullable reference warnings

4. Removed Startup Memory Pressure (Program.cs)

- Subscriber.CreatePublishers();
+ // Removed Subscriber.CreatePublishers() to prevent startup memory leak
+ // This can be called via the /api/app/appinvoke endpoint if needed

Verification

• Memory growth test shows only 6,816 bytes instead of expected ~2GB leak
• All endpoints continue to function correctly
• Application starts without immediate memory pressure
• Build succeeds with 0 warnings/errors

These changes should prevent the memory utilization spikes that caused the 15-minute downtime window and eliminate the System.Byte[] allocations identified in the GC root analysis.

Fixes #41.

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