feat: Permettre aux enseignants de contourner les règles de devoirs avec justification

Akeneo permet de configurer des règles de devoirs en mode Hard qui bloquent
totalement la création. Or certains cas légitimes (sorties scolaires, événements
exceptionnels) nécessitent de passer outre ces règles. Sans mécanisme d'exception,
l'enseignant est bloqué et doit contacter manuellement la direction.

Cette implémentation ajoute un flux complet d'exception : l'enseignant justifie
sa demande (min 20 caractères), le devoir est créé immédiatement, et la direction
est notifiée par email. Le handler vérifie côté serveur que les règles sont
réellement bloquantes avant d'accepter l'exception, empêchant toute fabrication
de fausses exceptions via l'API. La direction dispose d'un rapport filtrable
par période, enseignant et type de règle.

frontend/src/routes/dashboard/teacher/homework/+page.svelte

@@ -4,6 +4,7 @@
 	import { getApiBaseUrl } from '$lib/api/config';
 	import { authenticatedFetch, getAuthenticatedUserId } from '$lib/auth';
 	import Pagination from '$lib/components/molecules/Pagination/Pagination.svelte';
+	import ExceptionRequestModal from '$lib/components/molecules/ExceptionRequestModal/ExceptionRequestModal.svelte';
 	import RuleBlockedModal from '$lib/components/molecules/RuleBlockedModal/RuleBlockedModal.svelte';
 	import SearchInput from '$lib/components/molecules/SearchInput/SearchInput.svelte';
 	import { untrack } from 'svelte';
@@ -20,6 +21,9 @@
 		className: string | null;
 		subjectName: string | null;
 		hasRuleOverride: boolean;
+		hasRuleException?: boolean;
+		ruleExceptionJustification?: string | null;
+		ruleExceptionRuleType?: string | null;
 		createdAt: string;
 		updatedAt: string;
 	}
@@ -105,6 +109,15 @@
 	let ruleBlockedWarnings = $state<RuleWarning[]>([]);
 	let ruleBlockedSuggestedDates = $state<string[]>([]);
 
+	// Exception justification viewing
+	let showJustificationModal = $state(false);
+	let justificationHomework = $state<Homework | null>(null);
+
+	// Exception request modal
+	let showExceptionModal = $state(false);
+	let exceptionWarnings = $state<RuleWarning[]>([]);
+	let isSubmittingException = $state(false);
+
 	// Inline date validation for hard mode
 	let dueDateError = $state<string | null>(null);
 
@@ -452,6 +465,55 @@
 		showCreateModal = true;
 	}
 
+	function handleRequestException() {
+		exceptionWarnings = ruleBlockedWarnings;
+		showRuleBlockedModal = false;
+		showExceptionModal = true;
+	}
+
+	async function handleExceptionSubmit(justification: string, ruleTypes: string[]) {
+		if (!newClassId || !newSubjectId || !newTitle.trim() || !newDueDate) return;
+
+		try {
+			isSubmittingException = true;
+			error = null;
+			const apiUrl = getApiBaseUrl();
+			const response = await authenticatedFetch(`${apiUrl}/homework/with-exception`, {
+				method: 'POST',
+				headers: { 'Content-Type': 'application/json' },
+				body: JSON.stringify({
+					classId: newClassId,
+					subjectId: newSubjectId,
+					title: newTitle.trim(),
+					description: newDescription.trim() || null,
+					dueDate: newDueDate,
+					justification,
+					ruleTypes,
+				}),
+			});
+
+			if (!response.ok) {
+				const errorData = await response.json().catch(() => null);
+				const msg =
+					errorData?.['hydra:description'] ??
+					errorData?.message ??
+					errorData?.detail ??
+					`Erreur lors de la création avec exception (${response.status})`;
+				throw new Error(msg);
+			}
+
+			showExceptionModal = false;
+			exceptionWarnings = [];
+			ruleBlockedWarnings = [];
+			ruleBlockedSuggestedDates = [];
+			await loadHomeworks();
+		} catch (e) {
+			error = e instanceof Error ? e.message : 'Erreur lors de la création avec exception';
+		} finally {
+			isSubmittingException = false;
+		}
+	}
+
 	function handleBlockedClose() {
 		const firstSuggested = ruleBlockedSuggestedDates[0];
 		const conformDate = firstSuggested ?? computeConformMinDate(ruleBlockedWarnings);
@@ -717,7 +779,14 @@
 					<div class="homework-header">
 						<h3 class="homework-title">{hw.title}</h3>
 						<div class="homework-badges">
-							{#if hw.hasRuleOverride}
+							{#if hw.hasRuleException}
+								<button
+									type="button"
+									class="badge-rule-exception"
+									title="Créé avec une exception aux règles — cliquer pour voir la justification"
+									onclick={() => { justificationHomework = hw; showJustificationModal = true; }}
+								>&#9888; Exception</button>
+							{:else if hw.hasRuleOverride}
 								<span class="badge-rule-override" title="Créé malgré un avertissement de règle">&#9888;</span>
 							{/if}
 							<span class="homework-status" class:status-published={hw.status === 'published'} class:status-deleted={hw.status === 'deleted'}>
@@ -1158,9 +1227,63 @@
 		suggestedDates={ruleBlockedSuggestedDates}
 		onSelectDate={handleBlockedSelectDate}
 		onClose={handleBlockedClose}
+		onRequestException={handleRequestException}
 	/>
 {/if}
 
+<!-- Exception Request Modal -->
+{#if showExceptionModal && exceptionWarnings.length > 0}
+	<ExceptionRequestModal
+		warnings={exceptionWarnings}
+		onSubmit={handleExceptionSubmit}
+		onClose={() => {
+			showExceptionModal = false;
+			exceptionWarnings = [];
+		}}
+		isSubmitting={isSubmittingException}
+	/>
+{/if}
+
+<!-- Justification Viewing Modal -->
+{#if showJustificationModal && justificationHomework}
+	<!-- svelte-ignore a11y_no_static_element_interactions -->
+	<div class="modal-overlay" onclick={() => { showJustificationModal = false; justificationHomework = null; }} role="presentation">
+		<div
+			class="modal modal-confirm"
+			role="dialog"
+			aria-modal="true"
+			aria-labelledby="justification-title"
+			tabindex="-1"
+			onclick={(e) => e.stopPropagation()}
+			onkeydown={(e) => { if (e.key === 'Escape') { showJustificationModal = false; justificationHomework = null; } }}
+		>
+			<header class="modal-header modal-header-exception-view">
+				<h2 id="justification-title">Exception aux règles</h2>
+				<button class="modal-close" onclick={() => { showJustificationModal = false; justificationHomework = null; }} aria-label="Fermer">&times;</button>
+			</header>
+
+			<div class="modal-body">
+				<div class="justification-info">
+					<span class="justification-info-label">Devoir :</span>
+					<span>{justificationHomework.title}</span>
+					<span class="justification-info-label">Règle contournée :</span>
+					<span>{justificationHomework.ruleExceptionRuleType ?? 'N/A'}</span>
+				</div>
+				<div class="justification-content">
+					<span class="justification-content-label">Justification :</span>
+					<p class="justification-content-text">{justificationHomework.ruleExceptionJustification ?? 'Non disponible'}</p>
+				</div>
+			</div>
+
+			<div class="modal-actions">
+				<button type="button" class="btn-secondary" onclick={() => { showJustificationModal = false; justificationHomework = null; }}>
+					Fermer
+				</button>
+			</div>
+		</div>
+	</div>
+{/if}
+
 <style>
 	.homework-page {
 		padding: 1.5rem;
@@ -1713,6 +1836,73 @@
 		cursor: help;
 	}
 
+	.badge-rule-exception {
+		font-size: 0.7rem;
+		color: #92400e;
+		background: #fffbeb;
+		border: 1px solid #fde68a;
+		border-radius: 9999px;
+		padding: 0.125rem 0.5rem;
+		font-weight: 600;
+		cursor: pointer;
+		transition: all 0.2s;
+	}
+
+	.badge-rule-exception:hover {
+		background: #fef3c7;
+		border-color: #f59e0b;
+	}
+
+	/* Justification viewing modal */
+	.modal-header-exception-view {
+		background: #f59e0b;
+		color: white;
+		border-radius: 0.75rem 0.75rem 0 0;
+	}
+
+	.modal-header-exception-view h2 {
+		margin: 0;
+		font-size: 1.1rem;
+	}
+
+	.justification-info {
+		display: grid;
+		grid-template-columns: auto 1fr;
+		gap: 0.25rem 0.75rem;
+		padding: 0.75rem 1rem;
+		margin-bottom: 1rem;
+		background: #f9fafb;
+		border-radius: 0.375rem;
+		font-size: 0.875rem;
+	}
+
+	.justification-info-label {
+		font-weight: 600;
+		color: #374151;
+	}
+
+	.justification-content {
+		padding: 0.75rem 1rem;
+		background: #fffbeb;
+		border: 1px solid #fde68a;
+		border-radius: 0.375rem;
+	}
+
+	.justification-content-label {
+		font-size: 0.75rem;
+		font-weight: 600;
+		color: #92400e;
+		text-transform: uppercase;
+	}
+
+	.justification-content-text {
+		margin: 0.25rem 0 0;
+		font-size: 0.875rem;
+		color: #374151;
+		line-height: 1.5;
+		font-style: italic;
+	}
+
 	/* Rule Warning Modal */
 	.modal-header-warning {
 		border-bottom: 3px solid #f59e0b;