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-module-builder/SKILL.md

@@ -0,0 +1,32 @@
+---
+name: bmad-module-builder
+description: Plans, creates, and validates BMad modules. Use when the user requests to 'ideate module', 'plan a module', 'create module', 'build a module', or 'validate module'.
+---
+
+# BMad Module Builder
+
+## Overview
+
+This skill helps you bring BMad modules to life — from the first spark of an idea to a fully scaffolded, installable module. It offers three paths:
+
+- **Ideate Module (IM)** — A creative brainstorming session that helps you imagine what your module could be, decide on the right architecture (agent vs. workflow vs. both), and produce a detailed plan document. The plan then guides you through building each piece with the Agent Builder and Workflow Builder.
+- **Create Module (CM)** — Takes an existing folder of built skills and scaffolds the setup infrastructure (module.yaml, module-help.csv, setup skill) that makes it a proper installable BMad module. Supports `--headless` / `-H`.
+- **Validate Module (VM)** — Checks that a module's setup skill is complete and correct — every skill has its capabilities registered, entries are accurate and well-crafted, and structural integrity is sound.
+
+**Args:** Accepts `--headless` / `-H` for CM path only, an initial description for IM, or a path to a skills folder for CM/VM.
+
+## On Activation
+
+Load available config from `{project-root}/_bmad/config.yaml` and `{project-root}/_bmad/config.user.yaml` (root level and `bmb` section). If config is missing, let the user know `bmad-builder-setup` can configure the module at any time. Use sensible defaults for anything not configured.
+
+Detect user's intent:
+
+- **Ideate / Plan** keywords or no path argument → Load `./references/ideate-module.md`
+- **Create / Scaffold** keywords or a folder path → Load `./references/create-module.md`
+- **Validate / Check** keywords → Load `./references/validate-module.md`
+- **Unclear** → Present options:
+  - **Ideate Module (IM)** — "I have an idea for a module and want to brainstorm and plan it"
+  - **Create Module (CM)** — "I've already built my skills and want to package them as a module"
+  - **Validate Module (VM)** — "I want to check that my module's setup skill is complete and correct"
+
+If `--headless` or `-H` is passed, route to CM with headless mode.