docs: Add comprehensive TROUBLESHOOTING.md guide

[jadonamite]

### Overview This PR creates a new, extensive `TROUBLESHOOTING.md` guide for the repository. Currently, the repository lacks a centralized resource for debugging common runtime errors. This leads to repetitive issues regarding syncing, hardware requirements, and Docker misconfigurations. This PR fills that gap with a structured guide covering the most frequent operator pain points. ###Motivation & Context Node operators frequently encounter issues that are not bugs in the code, but environmental or configuration constraints. ***Context Deadline:** Users confuse disk bottlenecks with network errors. ***JWT Errors:** Docker volume mapping often leads to auth failures between `op-node` and execution clients. ***L1 Connection:** Derivation failures due to poor L1 RPC quality. Providing a centralized "Self-Help" document will reduce the support burden on maintainers and discord moderators. ### Content Included The new guide covers three main categories: 1.**Syncing & Performance:*** Detailed breakdown of the "Context Deadline Exceeded" error (IOPS vs Latency). * Snap sync behaviors ("Healing"). 2.**Configuration & Connectivity:*** Engine API (JWT) troubleshooting. * L1 RPC requirements and common failures. * P2P discovery (ports/firewalls). 3.**Docker & Operations:*** Permission denied errors on data volumes. ### Checklist-[x] Created `TROUBLESHOOTING.md`-[x] Covered hardware/IOPS requirements extensively. -[x] Included specific log signatures for easy `Ctrl+F` searching.

[cb-heimdall]

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