Add relay count tracking workflow with dual charts

This commit adds:
- New GitHub workflow to track relay counts
- Two charts: BitChat-compatible relays and total functioning relays
- Extended history for both charts (70 days)
- Project structure improvements with scripts and assets directories
- Updated documentation in README.md and other files
- Dependencies in requirements.txt

assets/README.md

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+# Georelays Assets
+
+This directory contains generated assets for the Georelays project:
+
+## bitchat_relay_count_chart.png
+
+A chart showing the history of the number of BitChat-compatible relays (supporting kind 20000 events) in the `nostr_relays.csv` file over time.
+
+## total_relay_count_chart.png
+
+A chart showing the history of the total number of functioning relays discovered in the `relay_discovery_results.json` file over time.
+
+These charts are automatically generated by the GitHub workflow after each update to the relay data.
+They track the last 30 changes to the relay lists and plot them on time series graphs.