Update dashboard

[bszaf]

Summary

Enhanced the Document Engine dashboard from 30 to 63 panels, adding comprehensive observability across all system components.

Changes

• Added 8 new sections: PostgreSQL, Redis Cache, Memory Cache, HTTP/2 Streaming, Remote Documents, Document Conversion, Digital Signatures, Queue Drops & Errors
• Split Erlang VM memory: Separate panels for Process, Binary, ETS, and Atom memory
• Added emojis: All 14 sections now have emoji prefixes for better navigation
• Optimized queries: Replaced delta() with increase() for counters, removed redundant filters
• Removed unused variable: Cleaned up erlang_memory_detail_metrics variable
• Better organization: Logical grouping of related metrics

New Metrics Covered

• PostgreSQL: query duration, connection pool, decode time
• Redis: cache hits/misses, operations, errors (when enabled)
• Memory cache: hit/miss rates and ratios
• HTTP/2: worker checkout time, render tile duration, process creation
• Remote documents: TTFB and download time
• Document conversion: conversion duration and rate
• Digital signatures: signing, certificates, timestamps (when enabled)
• Queue management: dropped requests and fallback hits