Add ruff linter/formatter for Python

- Add ruff as dev dependency
- Configure ruff in pyproject.toml with strict 88-char line limit
- Ignore B008 (FastAPI Depends pattern is standard)
- Allow longer lines in tests for readability
- Fix all lint issues in source files
- Add Makefile targets: lint-backend, format-backend, fix-backend

backend/validate_constants.py

@@ -1,8 +1,9 @@
 """Validate shared constants match backend definitions."""
+
 import json
 from pathlib import Path
 
-from models import ROLE_ADMIN, ROLE_REGULAR, InviteStatus, AppointmentStatus
+from models import ROLE_ADMIN, ROLE_REGULAR, AppointmentStatus, InviteStatus
 
 
 def validate_shared_constants() -> None:
@@ -11,13 +12,13 @@ def validate_shared_constants() -> None:
     Raises ValueError if there's a mismatch.
     """
     constants_path = Path(__file__).parent.parent / "shared" / "constants.json"
-    
+
     if not constants_path.exists():
         raise ValueError(f"Shared constants file not found: {constants_path}")
-    
+
     with open(constants_path) as f:
         constants = json.load(f)
-    
+
     # Validate roles
     expected_roles = {"ADMIN": ROLE_ADMIN, "REGULAR": ROLE_REGULAR}
     if constants.get("roles") != expected_roles:
@@ -25,39 +26,46 @@ def validate_shared_constants() -> None:
             f"Role mismatch in shared/constants.json. "
             f"Expected: {expected_roles}, Got: {constants.get('roles')}"
         )
-    
+
     # Validate invite statuses
     expected_invite_statuses = {s.name: s.value for s in InviteStatus}
     if constants.get("inviteStatuses") != expected_invite_statuses:
+        got = constants.get("inviteStatuses")
         raise ValueError(
-            f"Invite status mismatch in shared/constants.json. "
-            f"Expected: {expected_invite_statuses}, Got: {constants.get('inviteStatuses')}"
+            f"Invite status mismatch. Expected: {expected_invite_statuses}, Got: {got}"
         )
-    
+
     # Validate appointment statuses
     expected_appointment_statuses = {s.name: s.value for s in AppointmentStatus}
     if constants.get("appointmentStatuses") != expected_appointment_statuses:
+        got = constants.get("appointmentStatuses")
         raise ValueError(
-            f"Appointment status mismatch in shared/constants.json. "
-            f"Expected: {expected_appointment_statuses}, Got: {constants.get('appointmentStatuses')}"
+            f"Appointment status mismatch. "
+            f"Expected: {expected_appointment_statuses}, Got: {got}"
         )
-    
+
     # Validate booking constants exist with required fields
     booking = constants.get("booking", {})
-    required_booking_fields = ["slotDurationMinutes", "maxAdvanceDays", "minAdvanceDays", "noteMaxLength"]
+    required_booking_fields = [
+        "slotDurationMinutes",
+        "maxAdvanceDays",
+        "minAdvanceDays",
+        "noteMaxLength",
+    ]
     for field in required_booking_fields:
         if field not in booking:
-            raise ValueError(f"Missing booking constant '{field}' in shared/constants.json")
-    
+            raise ValueError(f"Missing booking constant '{field}' in constants.json")
+
     # Validate validation rules exist (structure check only)
     validation = constants.get("validation", {})
     required_fields = ["telegram", "signal", "nostrNpub"]
     for field in required_fields:
         if field not in validation:
-            raise ValueError(f"Missing validation rules for '{field}' in shared/constants.json")
+            raise ValueError(
+                f"Missing validation rules for '{field}' in constants.json"
+            )
 
 
 if __name__ == "__main__":
     validate_shared_constants()
     print("✓ Shared constants are valid")
-