fix: correct hashrate aggregation to compute per-tick fleet totals

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

fix: correct hashrate graph edge drops in 6h dashboard chart

Average hashrate across time ticks within each 5-min bucket instead of
summing, and use epoch-based bucket keys for correct midnight sorting.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

feat: add reboot-safe tarish server communication toggle

feat: add GitHub release package builds

feat: add tarish dashboard install guides