Add 1h pre-aggregated data, improve dashboards, and speed up web queries

[cchwala]

Changes

• TimescaleDB: Added cml_data_1h continuous aggregate (min/max/avg per sublink per hour) with an auto-refresh policy, reducing query load for historical data.
• Grafana real-time dashboard: Rewrote RSL/TSL panels to show a shaded min/max band with mean line. Automatically switches between raw data (≤3 days) and 1h aggregates (>3 days). Added an interval variable (Auto/Raw). Removed Altair dependency.
• Grafana archive dashboard: New cml-archive dashboard with two bar chart panels (active sublinks/hour and approximate data points/hour), embedded in the archive page via iframe.
• Webserver performance: Replaced full-table COUNT(*) with approximate_row_count(), replaced MIN/MAX(time) FROM cml_data with MIN/MAX(bucket) FROM cml_data_1h, and removed the per-CML GROUP BY stats query. Fully removed pandas and Altair from the webserver.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.18%. Comparing base (d136099) to head (5067a8a).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
webserver/main.py	0.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #27      +/-   ##
==========================================
+ Coverage   71.44%   73.18%   +1.73%     
==========================================
  Files          22       22              
  Lines        2021     1965      -56     
==========================================
- Hits         1444     1438       -6     
+ Misses        577      527      -50     

Flag	Coverage Δ
mno_simulator	84.18% <ø> (ø)
parser	77.91% <ø> (ø)
webserver	49.08% <0.00%> (+4.34%)	⬆️

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[cchwala]

Tested also on the machine which now was running the last main for 20 days and contains 125 million data records. The two steps from the migration document worked, but took several minutes to finish.

The real-time site takes approx a second to load, which is not perfect but good enough for now and for the time being. Switching between CMLs by clicking on them on the maps works instantly. It looks like that with 20 days of data: