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-quick-dev/step-02-plan.md

@@ -0,0 +1,35 @@
+---
+wipFile: '{implementation_artifacts}/spec-wip.md'
+deferred_work_file: '{implementation_artifacts}/deferred-work.md'
+---
+
+# Step 2: Plan
+
+## RULES
+
+- YOU MUST ALWAYS SPEAK OUTPUT in your Agent communication style with the config `{communication_language}`
+- No intermediate approvals.
+
+## INSTRUCTIONS
+
+1. Investigate codebase. _Isolate deep exploration in sub-agents/tasks where available. To prevent context snowballing, instruct subagents to give you distilled summaries only._
+2. Read `./spec-template.md` fully. Fill it out based on the intent and investigation, and write the result to `{wipFile}`.
+3. Self-review against READY FOR DEVELOPMENT standard.
+4. If intent gaps exist, do not fantasize, do not leave open questions, HALT and ask the human.
+5. Token count check (see SCOPE STANDARD). If spec exceeds 1600 tokens:
+   - Show user the token count.
+   - HALT and ask human: `[S] Split — carve off secondary goals` | `[K] Keep full spec — accept the risks`
+   - On **S**: Propose the split — name each secondary goal. Append deferred goals to `{deferred_work_file}`. Rewrite the current spec to cover only the main goal — do not surgically carve sections out; regenerate the spec for the narrowed scope. Continue to checkpoint.
+   - On **K**: Continue to checkpoint with full spec.
+
+### CHECKPOINT 1
+
+Present summary. If token count exceeded 1600 and user chose [K], include the token count and explain why it may be a problem. HALT and ask human: `[A] Approve` | `[E] Edit`
+
+- **A**: Rename `{wipFile}` to `{spec_file}`, set status `ready-for-dev`. Everything inside `<frozen-after-approval>` is now locked — only the human can change it. Display the finalized spec path to the user as a CWD-relative path (no leading `/`) so it is clickable in the terminal. → Step 3.
+- **E**: Apply changes, then return to CHECKPOINT 1.
+
+
+## NEXT
+
+Read fully and follow `./step-03-implement.md`