feat: add 17 new cross-exchange pairs (BG↔HL)

Added: ALGO, PYTH, SAND, ADA, HBAR, IOTA, MINA, FET, WLD,
       SUI, APT, NEAR, FIL, DYDX, JUP, TIA, MOVE

Removed: pixel and VET (fake 195% spreads on testnet)

Also updated GetHLSize() to handle szDecimals for all new coins.

check_db.py

@@ -0,0 +1,6 @@
+import sqlite3
+conn = sqlite3.connect('data/trades.db')
+rows = conn.execute('SELECT id, scale_count, amount_usd, fee_entry, fee_exit, net_pnl FROM trades').fetchall()
+for r in rows:
+    print(f'  #{r[0]}: scales={r[1]} amt=${r[2]} fee_entry={r[3]:.6f} fee_exit={r[4]:.6f} net={r[5]:.6f}')
+conn.close()