Fix duplicate 'now' declarations breaking dashboard JS

[skyelaird]

Summary

initializeDashboard() declared const now and const currentHour twice in the same scope (lines 1658 and 1672). Modern browsers reject this with a parse-time SyntaxError: Identifier 'now' has already been declared, which silently kills the entire <script> block — no event handlers get attached, no buttons work, and no /api/* calls are ever made even though dashboard.html renders.

The two uses had different semantics (fractional hour for grayLineSlider, integer hour for grayLineTimeSlider), so I renamed the second pair to currentHourInt and tickHour rather than dedupe.

Repro

1. pip install -e ".[dashboard]" and run dvoacap-dashboard.
2. Load http://localhost:8000 in any modern browser.
3. Open DevTools Console — observe the SyntaxError plus a cascade of triggerRefresh is not defined, showSettings is not defined, showTab is not defined ReferenceErrors.
4. Click any button: nothing happens, server log shows no /api/... request.

Test plan

• Open dashboard in browser, hard-reload, verify Console is clean.
• Click "Refresh Predictions" → server log shows POST /api/generate.
• Click tabs (Band Details, Propagation Charts, etc.) → tab content switches.

https://claude.ai/code/session_01PLeFRjjJUKnUAjA5imhsZz

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