Add batch valuation (POST /analytics/valuation/batch, max 50 properties),
valuation comparison (POST /analytics/valuation/compare, 2-5 properties),
and history endpoint (GET /analytics/valuation/history/:propertyId) with
confidence explanation helper. Frontend: enhanced valuation form with project
autocomplete and deep analysis toggle, results with confidence badges and
price range visualization, comparables table, history chart, market context
card, and PDF export.
Co-Authored-By: Paperclip <noreply@paperclip.ing>
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