Add gaming deals Matrix bot

Implements a Matrix bot that posts PC gaming deals and free game alerts:
- CheapShark API integration (Steam, GOG, Humble, GMG) polled every 2 hours
- Epic Games Store free games detection polled daily
- IsThereAnyDeal historical low price flagging (optional)
- SQLite deduplication with 30-day pruning
- First-run population (records existing deals without posting)
- Matrix-flavored HTML + plain text fallback messages
- Dockerfile for containerized deployment

https://claude.ai/code/session_01LPpSZFfyh6vdV5HGFWjoQX

.env.example

@@ -0,0 +1,16 @@
+# Matrix connection
+MATRIX_HOMESERVER_URL=https://matrix.example.com
+MATRIX_BOT_USER_ID=@dealsbot:example.com
+MATRIX_BOT_ACCESS_TOKEN=syt_...
+MATRIX_DEALS_ROOM_ID=!roomid:example.com
+
+# IsThereAnyDeal API key (optional — enables historical low detection)
+ITAD_API_KEY=
+
+# Deal filtering
+MIN_DEAL_RATING=80
+MIN_DISCOUNT_PERCENT=50
+MAX_PRICE_USD=20
+
+# Database path (inside the container, mount a volume for persistence)
+DATABASE_PATH=/data/deals.db