test(server): ajoute tests fonctionnels sync et fixtures versionnees (#187)

Fixe .gitignore pour exclure .build-home/ et .pub-cache-local/ des
environnements locaux de build (bruit non versionne). Documente le
checklist d'integration serveur et met a jour le README en consequence.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/test/fixtures/exercises/v1/with_timers.json

@@ -0,0 +1,18 @@
+{
+  "schemaVersion": 4,
+  "id": "exercise-with-timers",
+  "name": "Tempo bench press",
+  "type": "strength",
+  "timers": {
+    "preparationSeconds": 15,
+    "workSeconds": 45,
+    "restSeconds": 90,
+    "transitionSeconds": 10
+  },
+  "defaultTargets": {
+    "sets": 5,
+    "reps": 5,
+    "weightKg": 80
+  },
+  "updatedAt": "2026-07-19T10:15:00.000Z"
+}