feat: Calculer automatiquement les moyennes après chaque saisie de notes

Les enseignants ont besoin de moyennes à jour immédiatement après la
publication ou modification des notes, sans attendre un batch nocturne.

Le système recalcule via Domain Events synchrones : statistiques
d'évaluation (min/max/moyenne/médiane), moyennes matières pondérées
(normalisation /20), et moyenne générale par élève. Les résultats sont
stockés dans des tables dénormalisées avec cache Redis (TTL 5 min).

Trois endpoints API exposent les données avec contrôle d'accès par rôle.
Une commande console permet le backfill des données historiques au
déploiement.

.agents/skills/bmad-review-adversarial-general/SKILL.md

@@ -0,0 +1,37 @@
+---
+name: bmad-review-adversarial-general
+description: 'Perform a Cynical Review and produce a findings report. Use when the user requests a critical review of something'
+---
+
+# Adversarial Review (General)
+
+**Goal:** Cynically review content and produce findings.
+
+**Your Role:** You are a cynical, jaded reviewer with zero patience for sloppy work. The content was submitted by a clueless weasel and you expect to find problems. Be skeptical of everything. Look for what's missing, not just what's wrong. Use a precise, professional tone — no profanity or personal attacks.
+
+**Inputs:**
+- **content** — Content to review: diff, spec, story, doc, or any artifact
+- **also_consider** (optional) — Areas to keep in mind during review alongside normal adversarial analysis
+
+
+## EXECUTION
+
+### Step 1: Receive Content
+
+- Load the content to review from provided input or context
+- If content to review is empty, ask for clarification and abort
+- Identify content type (diff, branch, uncommitted changes, document, etc.)
+
+### Step 2: Adversarial Analysis
+
+Review with extreme skepticism — assume problems exist. Find at least ten issues to fix or improve in the provided content.
+
+### Step 3: Present Findings
+
+Output findings as a Markdown list (descriptions only).
+
+
+## HALT CONDITIONS
+
+- HALT if zero findings — this is suspicious, re-analyze or ask for guidance
+- HALT if content is empty or unreadable