Add doc for workers architecture

assets/documentation/Workers processing/02-Request-Flow.md

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+# Request Flow Sequence Diagram
+
+This diagram shows the complete request flow from user submission to job completion and status polling.
+
+```mermaid
+sequenceDiagram
+    participant User
+    participant API as API Server<br/>(Orleans)
+    participant DB as PostgreSQL<br/>(Job Queue)
+    participant Worker as Compute Worker
+    participant Influx as InfluxDB
+    
+    User->>API: POST /api/backtest/bundle
+    API->>API: Create BundleBacktestRequest
+    API->>API: Generate BacktestJobs from variants
+    API->>DB: INSERT BacktestJobs (Status: Pending)
+    API-->>User: 202 Accepted<br/>{bundleRequestId, status: "Queued"}
+    
+    Note over Worker: Polling every 5 seconds
+    Worker->>DB: SELECT pending jobs<br/>(ORDER BY priority, createdAt)
+    DB-->>Worker: Return pending jobs
+    Worker->>DB: UPDATE job<br/>(Status: Running, AssignedWorkerId)
+    Worker->>Influx: Load candles for backtest
+    Influx-->>Worker: Return candles
+    
+    loop Process each candle
+        Worker->>Worker: Run backtest logic
+        Worker->>DB: UPDATE job progress
+    end
+    
+    Worker->>DB: UPDATE job<br/>(Status: Completed, ResultJson)
+    Worker->>DB: UPDATE BundleBacktestRequest<br/>(CompletedBacktests++)
+    
+    User->>API: GET /api/backtest/bundle/{id}/status
+    API->>DB: SELECT BundleBacktestRequest + job stats
+    DB-->>API: Return status
+    API-->>User: {status, progress, completed/total}
+```
+
+## Flow Steps
+
+1. **User Request**: User submits bundle backtest request
+2. **API Processing**: API creates bundle request and generates individual backtest jobs
+3. **Job Queue**: Jobs are inserted into database with `Pending` status
+4. **Immediate Response**: API returns 202 Accepted with bundle request ID
+5. **Worker Polling**: Compute workers poll database every 5 seconds
+6. **Job Claiming**: Worker claims jobs using PostgreSQL advisory locks
+7. **Candle Loading**: Worker loads candles from InfluxDB
+8. **Backtest Processing**: Worker processes backtest with progress updates
+9. **Result Storage**: Worker saves results and updates bundle progress
+10. **Status Polling**: User polls API for status updates
+