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)

data/metadata/generation_metadata.json

@@ -1,5 +1,5 @@
 {
-  "generated_at": "2026-02-10T16:10:43.522420",
+  "generated_at": "2026-02-10T17:49:15.839052",
   "datasets": {
     "battery_capacity": {
       "rows": 144010,
@@ -84,6 +84,44 @@
         "max_bid_price": "float64",
         "client_type": "object"
       }
+    },
+    "transmission_capacity": {
+      "rows": 20,
+      "columns": [
+        "source_region",
+        "target_region",
+        "capacity_mw",
+        "direction",
+        "efficiency"
+      ],
+      "memory_usage_mb": 0.004016876220703125,
+      "dtypes": {
+        "source_region": "object",
+        "target_region": "object",
+        "capacity_mw": "float64",
+        "direction": "object",
+        "efficiency": "float64"
+      }
+    },
+    "transmission_cost": {
+      "rows": 20,
+      "columns": [
+        "source_region",
+        "target_region",
+        "cost_eur_mwh",
+        "loss_percent",
+        "congestion_surcharge_eur_mwh",
+        "fee_eur_mwh"
+      ],
+      "memory_usage_mb": 0.002986907958984375,
+      "dtypes": {
+        "source_region": "object",
+        "target_region": "object",
+        "cost_eur_mwh": "float64",
+        "loss_percent": "float64",
+        "congestion_surcharge_eur_mwh": "float64",
+        "fee_eur_mwh": "float64"
+      }
     }
   }
 }