fix(M4): pronote_url + account_type et parsing iCal (STATUS:CANCELLED + blocs multi-dates)

Configuration (D1+D3) :
- PronoteSettings : ajout pronote_url (str | None) et account_type
  (Literal student/parent, défaut parent)

Parsing iCal (Fix 4+7) :
- parse_ical : détection STATUS:CANCELLED en plus de CATEGORIES
- parse_body : list[tuple[date, str]] au lieu de dict[date, str]
  pour préserver les blocs multiples à la même date
- parse_homework_blocks : adapté aux listes

Co-authored-by: opencode/coder <coder@agents.invalid>

pronote_sync/config/settings.py

@@ -27,6 +27,8 @@ class PronoteSettings(BaseSettings):
     username: str | None = None
     password: SecretStr | None = None
     ent: str | None = None
+    pronote_url: str | None = None
+    account_type: Literal["student", "parent"] = "parent"
     agenda_source: Literal["auto", "ical", "pronotepy"] = "auto"
     homework_source: Literal["auto", "ical", "pronotepy"] = "auto"
     messages_source: Literal["pronotepy"] = "pronotepy"