feat: Add per-month rate override for adult fees

Mirror the junior fee override mechanism (JUNIOR_MONTHLY_RATE) for adults
via ADULT_FEE_MONTHLY_RATE. Set 2026-03 override to 350 CZK. Rename
FEE_FULL/FEE_SINGLE to ADULT_FEE_DEFAULT/ADULT_FEE_SINGLE for consistency.

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

scripts/attendance.py

@@ -10,8 +10,11 @@ from config import ATTENDANCE_SHEET_ID as SHEET_ID, JUNIOR_SHEET_GID
 EXPORT_URL = f"https://docs.google.com/spreadsheets/d/{SHEET_ID}/export?format=csv&gid=0"
 JUNIOR_EXPORT_URL = f"https://docs.google.com/spreadsheets/d/{SHEET_ID}/export?format=csv&gid={JUNIOR_SHEET_GID}"
 
-FEE_FULL = 750  # CZK, for 2+ practices in a month
-FEE_SINGLE = 200  # CZK, for exactly 1 practice in a month
+ADULT_FEE_DEFAULT = 750  # CZK, for 2+ practices in a month
+ADULT_FEE_SINGLE = 200  # CZK, for exactly 1 practice in a month
+ADULT_FEE_MONTHLY_RATE = {
+    "2026-03": 350
+}
 
 JUNIOR_FEE_DEFAULT = 500  # CZK for 2+ practices
 JUNIOR_MONTHLY_RATE = {
@@ -76,13 +79,13 @@ def group_by_month(dates: list[tuple[int, datetime]], merged_months: dict[str, s
     return months
 
 
-def calculate_fee(attendance_count: int) -> int:
-    """Apply fee rules: 0 → 0, 1 → 200, 2+ → 750."""
+def calculate_fee(attendance_count: int, month_key: str) -> int:
+    """Apply fee rules: 0 → 0, 1 → 200, 2+ → configured rate (default 750)."""
     if attendance_count == 0:
         return 0
     if attendance_count == 1:
-        return FEE_SINGLE
-    return FEE_FULL
+        return ADULT_FEE_SINGLE
+    return ADULT_FEE_MONTHLY_RATE.get(month_key, ADULT_FEE_DEFAULT)
 
 
 def calculate_junior_fee(attendance_count: int, month_key: str) -> str | int:
@@ -186,7 +189,7 @@ def get_members_with_fees() -> tuple[list[tuple[str, str, dict[str, int]]], list
                 for c in cols
                 if c < len(row) and row[c].strip().upper() == "TRUE"
             )
-            fee = calculate_fee(count) if tier == "A" else 0
+            fee = calculate_fee(count, month_key) if tier == "A" else 0
             month_fees[month_key] = (fee, count)
         members.append((name, tier, month_fees))