Add doc for workers architecture

assets/documentation/Workers processing/06-Concurrency-Control.md

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+# Concurrency Control Flow
+
+This diagram shows how the semaphore-based concurrency control works across multiple workers.
+
+```mermaid
+graph LR
+    subgraph "Database Queue"
+        Q[Pending Jobs<br/>Priority Queue]
+    end
+    
+    subgraph "Worker-1"
+        S1[Semaphore<br/>6 slots]
+        J1[Job 1]
+        J2[Job 2]
+        J3[Job 3]
+        J4[Job 4]
+        J5[Job 5]
+        J6[Job 6]
+    end
+    
+    subgraph "Worker-2"
+        S2[Semaphore<br/>6 slots]
+        J7[Job 7]
+        J8[Job 8]
+        J9[Job 9]
+        J10[Job 10]
+        J11[Job 11]
+        J12[Job 12]
+    end
+    
+    subgraph "Worker-3"
+        S3[Semaphore<br/>6 slots]
+        J13[Job 13]
+        J14[Job 14]
+        J15[Job 15]
+        J16[Job 16]
+        J17[Job 17]
+        J18[Job 18]
+    end
+    
+    Q -->|Claim 6 jobs| S1
+    Q -->|Claim 6 jobs| S2
+    Q -->|Claim 6 jobs| S3
+    
+    S1 --> J1
+    S1 --> J2
+    S1 --> J3
+    S1 --> J4
+    S1 --> J5
+    S1 --> J6
+    
+    S2 --> J7
+    S2 --> J8
+    S2 --> J9
+    S2 --> J10
+    S2 --> J11
+    S2 --> J12
+    
+    S3 --> J13
+    S3 --> J14
+    S3 --> J15
+    S3 --> J16
+    S3 --> J17
+    S3 --> J18
+    
+    style Q fill:#FF6B6B
+    style S1 fill:#50C878
+    style S2 fill:#50C878
+    style S3 fill:#50C878
+```
+
+## Concurrency Control Mechanisms
+
+### 1. Database-Level (Advisory Locks)
+- **PostgreSQL Advisory Locks**: Prevent multiple workers from claiming the same job
+- Atomic job claiming using `pg_try_advisory_lock()`
+- Ensures exactly-once job processing
+
+### 2. Worker-Level (Semaphore)
+- **SemaphoreSlim**: Limits concurrent backtests per worker
+- Default: `Environment.ProcessorCount - 2` (e.g., 6 on 8-core machine)
+- Prevents CPU saturation while leaving resources for Orleans messaging
+
+### 3. Cluster-Level (Queue Priority)
+- **Priority Queue**: Jobs ordered by priority, then creation time
+- VIP users get higher priority
+- Fair distribution across workers
+
+## Capacity Calculation
+
+- **Per Worker**: 6 concurrent backtests
+- **3 Workers**: 18 concurrent backtests
+- **Average Duration**: ~47 minutes per backtest
+- **Throughput**: ~1,080 backtests/hour
+- **1000 Users × 10 backtests**: ~9 hours to process full queue
+