fix: clear stale empty-state and grid content on new search

[nancysangani]

Fixes #730

setLoadingState and renderResults in script.js did not fully reset all three result sub-states (#results-loading, #results-empty, #results-grid) before each transition, causing the "No Projects Found" card to persist visually during a subsequent search.

Changes:

• static/script.js — setLoadingState(true) now clears resultsGrid.innerHTML and resultsEmptyEl.textContent before showing the spinner; renderResults resets both display states and guards emptyMessageEl against null before branching on result count
• tests/test_no_results_reset.py — 20 tests covering API state independence, alternating no-match/match sequences, HTML landmark presence, and the two JS fixes

[vercel]

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[nancysangani]

Hi @komalharshita, please review the PR when you get a chance. Thanks!