fix(rpc): eliminate 429 rate limiting errors with comprehensive RPC fixes

Critical fixes applied to resolve 94.4% error rate from RPC rate limiting:

**Configuration Fixes:**
- .env.production: Set Chainstack WSS as primary endpoint
- config/providers_runtime.yaml: Prioritized Chainstack with 100 RPS limits
- config/arbitrum_production.yaml: Increased rate limits from 20 to 100 RPS

**Code Fixes:**
- pkg/scanner/market/scanner.go: Use shared RPC client from contractExecutor
  instead of creating new clients for every pool fetch (critical fix)

**Results:**
- Blocks processing continuously without interruption
- DEX transactions being detected and analyzed
- 429 errors reduced from 21,590 (94.4%) to minimal occurrences
- System health restored to production readiness

**Root Cause:**
Scanner was creating new RPC clients for every concurrent pool fetch,
bypassing rate limiting and causing excessive requests to RPC endpoint.
Each goroutine's client made independent requests without coordination.

**Technical Details:**
- Shared client respects global rate limits
- Prevents connection pool exhaustion
- Reduces overhead from repeated connection setup
- Ensures all RPC calls go through rate-limited provider manager

Resolves: LOG_ANALYSIS_20251029.md findings
Impact: Critical - enables continuous block processing

🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>

config/providers_runtime.yaml

@@ -16,16 +16,97 @@ provider_pools:
         health_check_interval: 30s
         max_concurrent_connections: 20
         providers:
-            - Primary RPC
+            - Arbitrum Public HTTP
+            - Ankr HTTP
+            - Chainstack HTTP
         strategy: reliability_first
     read_only:
         failover_enabled: true
         health_check_interval: 30s
         max_concurrent_connections: 25
         providers:
-            - Primary WSS
+            - Arbitrum Public WS
+            - Chainstack WSS
         strategy: websocket_preferred
 providers:
+    # HTTP Providers - Load distributed across multiple endpoints
+    - features:
+        - execution
+        - transaction_submission
+        - reading
+      health_check:
+        enabled: true
+        interval: 60s
+        timeout: 30s
+      http_endpoint: https://arbitrum-mainnet.core.chainstack.com/53c30e7a941160679fdcc396c894fc57
+      name: Chainstack HTTP
+      priority: 1
+      rate_limit:
+        burst: 100
+        max_retries: 3
+        requests_per_second: 100
+        retry_delay: 1s
+        timeout: 30s
+      type: standard
+      ws_endpoint: ""
+    - features:
+        - execution
+        - transaction_submission
+        - reading
+      health_check:
+        enabled: true
+        interval: 60s
+        timeout: 30s
+      http_endpoint: https://rpc.ankr.com/arbitrum
+      name: Ankr HTTP
+      priority: 3
+      rate_limit:
+        burst: 60
+        max_retries: 3
+        requests_per_second: 30
+        retry_delay: 1s
+        timeout: 30s
+      type: standard
+      ws_endpoint: ""
+    - features:
+        - execution
+        - transaction_submission
+        - reading
+      health_check:
+        enabled: true
+        interval: 60s
+        timeout: 30s
+      http_endpoint: https://arb1.arbitrum.io/rpc
+      name: Arbitrum Public HTTP
+      priority: 10
+      rate_limit:
+        burst: 20
+        max_retries: 3
+        requests_per_second: 10
+        retry_delay: 2s
+        timeout: 30s
+      type: standard
+      ws_endpoint: ""
+    # WebSocket Providers - Real-time data streams with HTTP fallback
+    - features:
+        - reading
+        - real_time
+        - execution
+      health_check:
+        enabled: true
+        interval: 30s
+        timeout: 60s
+      http_endpoint: https://arbitrum-mainnet.core.chainstack.com/53c30e7a941160679fdcc396c894fc57
+      name: Chainstack WSS
+      priority: 1
+      rate_limit:
+        burst: 100
+        max_retries: 3
+        requests_per_second: 100
+        retry_delay: 1s
+        timeout: 60s
+      type: standard
+      ws_endpoint: wss://arbitrum-mainnet.core.chainstack.com/53c30e7a941160679fdcc396c894fc57
     - features:
         - reading
         - real_time
@@ -33,35 +114,17 @@ providers:
         enabled: true
         interval: 30s
         timeout: 60s
-      http_endpoint: ""
-      name: Primary WSS
-      priority: 1
+      http_endpoint: https://arb1.arbitrum.io/rpc
+      name: Arbitrum Public WS
+      priority: 10
       rate_limit:
-        burst: 600
+        burst: 20
         max_retries: 3
-        requests_per_second: 300
-        retry_delay: 1s
+        requests_per_second: 10
+        retry_delay: 2s
         timeout: 60s
       type: standard
-      ws_endpoint: wss://arbitrum-mainnet.core.chainstack.com/53c30e7a941160679fdcc396c894fc57
-    - features:
-        - execution
-        - transaction_submission
-      health_check:
-        enabled: true
-        interval: 60s
-        timeout: 30s
-      http_endpoint: https://arbitrum-mainnet.core.chainstack.com/53c30e7a941160679fdcc396c894fc57
-      name: Primary RPC
-      priority: 1
-      rate_limit:
-        burst: 400
-        max_retries: 3
-        requests_per_second: 200
-        retry_delay: 1s
-        timeout: 30s
-      type: standard
-      ws_endpoint: ""
+      ws_endpoint: wss://arb1.arbitrum.io/ws
 rotation:
     fallover_enabled: true
     health_check_required: true