feat(auth): politique de complexite du mot de passe et flux de reinitialisation

Remplace la regle de longueur seule (12 caracteres) par une exigence de
composition (8 caracteres minimum, majuscule, minuscule, chiffre, caractere
special), non documentee dans les exigences officielles du projet, par une
regle explicite partagee entre le backend (validateur Pydantic) et le
frontend.

Ajoute un flux "mot de passe oublie" en libre-service, absent jusqu'ici :
jeton a usage unique hache en base (meme principe que les refresh tokens),
expirant a 15 minutes, envoye par email via un service SMTP (aiosmtplib,
Mailpit en dev), avec limitation de debit dediee et reponse generique pour
eviter l'enumeration des comptes.

Closes #87

apps/backend/app/api/v1/endpoints/auth.py

@@ -12,6 +12,7 @@ from app.api.deps import (
     require_trusted_origin,
 )
 from app.api.openapi import (
+    REPONSE_LIMITE,
     REPONSE_ORIGINE_REFUSEE,
     REPONSE_VALIDATION,
     REPONSES_AUTHENTIFIEES,
@@ -21,15 +22,18 @@ from app.api.openapi import (
 from app.core.cookies import RefreshCookie, cookie_name
 from app.core.logging import get_logger
 from app.schemas.auth import (
+    ForgotPasswordRequest,
     LoginRequest,
     PasswordChangeRequest,
     PrincipalResponse,
+    ResetPasswordRequest,
     TokenResponse,
 )
 from app.schemas.errors import ErrorResponse
 from app.services.auth import (
     AuthenticatedSession,
     InvalidCredentialsError,
+    InvalidOrExpiredResetTokenError,
     RateLimitedError,
     SessionRejectedError,
 )
@@ -39,6 +43,7 @@ logger = get_logger(__name__)
 
 DETAIL_IDENTIFIANTS = "Identifiants invalides"
 DETAIL_SESSION = "Session invalide"
+DETAIL_LIEN_RESET = "Lien invalide ou expiré"
 
 REPONSES_LOGIN: Reponses = {
     **REPONSE_VALIDATION,
@@ -85,6 +90,20 @@ REPONSES_MOT_DE_PASSE: Reponses = {
     },
 }
 
+REPONSES_FORGOT_PASSWORD: Reponses = {
+    **REPONSE_VALIDATION,
+    **REPONSE_LIMITE,
+}
+
+REPONSES_RESET_PASSWORD: Reponses = {
+    **REPONSE_VALIDATION,
+    **REPONSE_ORIGINE_REFUSEE,
+    400: {
+        "model": ErrorResponse,
+        "description": "Lien invalide, déjà utilisé, ou expiré (durée de vie : 15 minutes).",
+    },
+}
+
 
 def repond(
     response: Response, settings: SettingsDep, session: AuthenticatedSession
@@ -267,3 +286,67 @@ async def change_password(
 
     logger.info("auth.password_changed user_id=%s", principal.id)
     return repond(response, settings, session)
+
+
+@router.post(
+    "/forgot-password",
+    status_code=status.HTTP_202_ACCEPTED,
+    summary="Demande un lien de réinitialisation par email",
+    responses=REPONSES_FORGOT_PASSWORD,
+)
+async def forgot_password(
+    payload: ForgotPasswordRequest,
+    request: Request,
+    response: Response,
+    service: AuthServiceDep,
+    client_ip: str | None = Depends(get_client_ip),
+) -> None:
+    response.headers["Cache-Control"] = "no-store"
+
+    try:
+        await service.request_password_reset(
+            email=payload.email,
+            client_ip=client_ip,
+            user_agent=request.headers.get("user-agent"),
+        )
+    except RateLimitedError as erreur:
+        logger.warning("auth.password_reset.rate_limited ip=%s", client_ip)
+        raise HTTPException(
+            status_code=status.HTTP_429_TOO_MANY_REQUESTS,
+            detail="Trop de demandes, réessayez plus tard",
+            headers={"Retry-After": str(erreur.retry_after)},
+        ) from erreur
+
+
+@router.post(
+    "/reset-password",
+    response_model=TokenResponse,
+    summary="Choisit un nouveau mot de passe depuis un lien reçu par email",
+    dependencies=[Depends(require_trusted_origin)],
+    responses=REPONSES_RESET_PASSWORD,
+)
+async def reset_password(
+    payload: ResetPasswordRequest,
+    request: Request,
+    response: Response,
+    settings: SettingsDep,
+    service: AuthServiceDep,
+    client_ip: str | None = Depends(get_client_ip),
+) -> TokenResponse:
+    response.headers["Cache-Control"] = "no-store"
+
+    try:
+        session = await service.confirm_password_reset(
+            token=payload.token,
+            new_password=payload.new_password,
+            client_ip=client_ip,
+            user_agent=request.headers.get("user-agent"),
+        )
+    except InvalidOrExpiredResetTokenError as erreur:
+        logger.warning("auth.password_reset.invalid_token ip=%s", client_ip)
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST, detail=DETAIL_LIEN_RESET
+        ) from erreur
+
+    logger.info("auth.password_reset.success user_id=%s", session.principal.id)
+    return repond(response, settings, session)