Multiple tune-ups, fixes and feature add-ons

[v-ivanyshyn]

Summary

• Improves live CAN visibility, monitoring accuracy, mutation workflow, DBC lifecycle, and offline-first UI documentation.

Live frames

• Show one row per CAN ID (no 40-row cap), with byte-level change highlighting instead of a ring-style stream.

Mutations

• Single-shot (“Once”) mode: apply on one frame, then disable; per-rule and bulk controls.
• Stage without immediate apply; rules are turned on from Active Mutations as needed.
• POST remove endpoint for individual rules/mutations.

Live Frames Changes (new feature)

• Watch per-byte churn on forwarded traffic, baseline stable bytes after the first “fix”, then diff live traffic vs that snapshot (firmware + UI).

Editors & DBC

• Stop auto-refreshing the mutation editor and raw frame/bit editor during status polls so in-progress edits are not cleared.
• Add DBC unload (API/UI).

Stats & latency

• Bus utilization for buses A and B (RX and TX) and hardware drop counters.
• Forwarding latency derived from RX timestamps, shown as a ~last-second window (not lifetime averages).

UI / assets / docs

• Layout tweaks for mobile & desktop.
• Remove external font/CSS imports so the ESP-hosted UI works without internet.
• README and screenshots updated.