Use CheapShark's native 0-10 scale for MIN_DEAL_RATING

The previous 0-100 scale with a * 10 conversion was confusing —
CheapShark returns deal ratings as floats (e.g. 9.8, 7.5) so the
config should match. Default is now 8.0 instead of 80.

https://claude.ai/code/session_01LPpSZFfyh6vdV5HGFWjoQX

.env.example

@@ -8,7 +8,7 @@ MATRIX_DEALS_ROOM_ID=!roomid:example.com
 ITAD_API_KEY=
 
 # Deal filtering
-MIN_DEAL_RATING=80
+MIN_DEAL_RATING=8.0
 MIN_DISCOUNT_PERCENT=50
 MAX_PRICE_USD=20