Add transmission datasets and update mining data

Add two new static datasets for cross-region arbitrage calculations:
- transmission_capacity: region-to-region capacity limits (20 rows)
- transmission_cost: transmission costs per path (20 rows)

Update mining dataset with EUR pricing and power metrics:
- Change btc_price_usd to btc_price_eur
- Add power_efficiency_th_per_mw, power_demand_mw
- Add revenue_eur_per_mwh, profit_eur_per_mwh
- Remove mining_profitability column

Changes include:
- scripts/02_fetch_historical.py: rewrite fetch_bitcoin_mining_data()
- scripts/01_generate_synthetic.py: add transmission data generators
- config/data_config.yaml: add transmission config, update bitcoin config
- config/schema.yaml: add 2 new schemas, update bitcoin_mining schema
- scripts/03_process_merge.py: add 2 new datasets
- scripts/04_validate.py: add 2 new datasets
- test/test_data.py: update for new datasets and bitcoin price reference

Total datasets: 9 (734,491 rows, 17.89 MB)

scripts/04_validate.py

@@ -233,7 +233,9 @@ def main():
         'conventional_generation',
         'load_profiles',
         'data_centers',
-        'bitcoin_mining'
+        'bitcoin_mining',
+        'transmission_capacity',
+        'transmission_cost'
     ]
     
     print("Validating processed datasets...\n")