feat: TOML config loader for vehicles, journeys, and tax scales

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

config.toml

@@ -0,0 +1,52 @@
+[vehicles.voiture]
+name = "Peugeot 308"
+fuel = "diesel"
+co2_per_km = 142
+cv = 5
+
+[vehicles.velo]
+name = "Vélo"
+fuel = "none"
+co2_per_km = 0
+
+[journeys.voiture_seule]
+name = "Voiture seule"
+distances = { voiture = 25 }
+
+[journeys.voiture_velo]
+name = "Voiture + Vélo"
+distances = { voiture = 14, velo = 8 }
+
+[journeys.velo_seul]
+name = "Vélo seul"
+distances = { velo = 24 }
+
+[[bareme_kilometrique.2025.cv_5.tranches]]
+km_max = 3000
+taux = 0.548
+forfait = 0
+
+[[bareme_kilometrique.2025.cv_5.tranches]]
+km_max = 6000
+taux = 0.316
+forfait = 699
+
+[[bareme_kilometrique.2025.cv_5.tranches]]
+km_max = 0
+taux = 0.364
+forfait = 0
+
+[[bareme_kilometrique.2025.cv_6_7.tranches]]
+km_max = 3000
+taux = 0.655
+forfait = 0
+
+[[bareme_kilometrique.2025.cv_6_7.tranches]]
+km_max = 6000
+taux = 0.374
+forfait = 836
+
+[[bareme_kilometrique.2025.cv_6_7.tranches]]
+km_max = 0
+taux = 0.435
+forfait = 0