add price tracking to collections and implement total value calculation

supabase/migrations/20250127000000_add_price_to_collections.sql

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+-- Add price_usd column to collections table
+ALTER TABLE collections
+ADD COLUMN IF NOT EXISTS price_usd DECIMAL(10, 2) DEFAULT 0;
+
+-- Create index for faster price calculations
+CREATE INDEX IF NOT EXISTS idx_collections_price ON collections(price_usd);
+
+-- Add comment
+COMMENT ON COLUMN collections.price_usd IS 'USD price of the card at time of addition/update';