Implémente système multi-utilisateurs avec classement

- Auth cookie simple (SSO-ready) : login/logout, redirection si non authentifié
- Données isolées par utilisateur dans /data/users/{user_id}/
- Migration automatique des données legacy au premier login
- Page classement avec podium et tableau comparatif (score, précision zéro, conformité)
- Nav mise à jour : Classement, affichage utilisateur courant, déconnexion

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

app/stats.py

@@ -50,9 +50,9 @@ def _compliance_over(all_days: list[tuple], cg_set: set) -> dict:
     return {"pct": round(100 * n_ok / n) if n else None, "n": n, "n_ok": n_ok}
 
 
-def compute_all_stats() -> dict:
-    all_weeks = sorted(list_all_weeks())
-    conges = load_conges()
+def compute_all_stats(user_id: str = "") -> dict:
+    all_weeks = sorted(list_all_weeks(user_id))
+    conges = load_conges(user_id)
     h_jour = int(float(load_config().get("heures_jour", 7.8)) * 60)
     cg_set = {(c["date"], c["type"]) for c in conges}
 
@@ -63,7 +63,6 @@ def compute_all_stats() -> dict:
     current_ym = (today.year, today.month)
 
     SLOTS = ["matin_entree", "matin_sortie", "aprem_entree", "aprem_sortie"]
-    # Store (value, date) pairs per slot
     slot_pairs: dict[str, list[tuple[int, str]]] = {s: [] for s in SLOTS}
     comp_n = {s: 0 for s in SLOTS}
     comp_ok = {s: 0 for s in SLOTS}
@@ -81,7 +80,7 @@ def compute_all_stats() -> dict:
     prev_week_day_list: list[tuple] = []
 
     for year, week in all_weeks:
-        raw = load_week_pointages(year, week)
+        raw = load_week_pointages(year, week, user_id)
         if not raw:
             continue
 
@@ -136,7 +135,7 @@ def compute_all_stats() -> dict:
         weekly_balances.append({
             "year": year, "week": week,
             "label": f"S{week:02d}",
-            "date": dates[0],  # Monday — used for period filtering
+            "date": dates[0],
             "delta_min": week_delta,
             "delta": minutes_to_hhmm(week_delta),
             "partial": week_has_incomplete,
@@ -163,7 +162,6 @@ def compute_all_stats() -> dict:
         for slot in comp_n
     }
     rates = [v for v in compliance.values() if v is not None]
-    overall_slot = round(sum(rates) / len(rates)) if rates else None
 
     n_jours = max(len(slot_pairs["matin_entree"]), len(slot_pairs["aprem_entree"]))
     deltas = [b["delta_min"] for b in weekly_balances]
@@ -176,7 +174,6 @@ def compute_all_stats() -> dict:
     return {
         "time_stats": time_stats,
         "compliance": compliance,
-        "overall_compliance": overall_slot,
         "weekly_balances": weekly_balances,
         "total_weeks": len(weekly_balances),
         "n_jours": n_jours,