feat(docker): rename web service to app, add nginx as web

Reorganize Docker Compose services: the Django/gunicorn container is now
`app` and nginx is `web`, better reflecting their roles. Add a dedicated
gunicorn configuration and install curl in the runtime image for health
checks.

Update documentation to reflect:
- Neo4j migration from ariel.incus to a dedicated umbriel.incus instance
- Rationale for requiring a dedicated Neo4j instance (single-tenancy
  assumptions, label/index isolation, schema ownership)
- New service naming in compose commands and log tailing examples

mnemosyne/.env example

@@ -18,7 +18,9 @@ DB_HOST=portia.incus
 DB_PORT=5432
 
 # --- Neo4j Graph Database ---
-NEOMODEL_NEO4J_BOLT_URL=bolt://neo4j:password@ariel.incus:25554
+# Dedicated Mnemosyne instance on Umbriel — do not share with Spelunker or any
+# other graph workload. See README.md for the full rationale.
+NEOMODEL_NEO4J_BOLT_URL=bolt://neo4j:password@umbriel.incus:7687
 
 # --- Memcached ---
 KVDB_LOCATION=127.0.0.1:11211

mnemosyne/mnemosyne/urls.py

@@ -8,6 +8,9 @@ from django.urls import include, path
 from . import views
 
 urlpatterns = [
+    # Health checks — no auth, must return 200 (not redirect) — use trailing slash
+    path("live/", views.live, name="live"),
+    path("ready/", views.ready, name="ready"),
     # Landing / Dashboard
     path("", views.landing, name="landing"),
     path("dashboard/", views.dashboard, name="dashboard"),

mnemosyne/mnemosyne/views.py

@@ -3,6 +3,9 @@ Mnemosyne project-level views — landing page and dashboard.
 """
 
 from django.contrib.auth.decorators import login_required
+from django.core.cache import cache
+from django.db import connection
+from django.http import JsonResponse
 from django.shortcuts import render
 
 from llm_manager.models import LLMApi, LLMModel
@@ -43,3 +46,22 @@ def dashboard(request):
         context["library_count"] = None
 
     return render(request, "mnemosyne/dashboard.html", context)
+
+
+def live(request):
+    return JsonResponse({"status": "ok"})
+
+
+def ready(request):
+    errors = {}
+    try:
+        connection.ensure_connection()
+    except Exception as e:
+        errors["db"] = str(e)
+    try:
+        cache.get("__readiness_probe__")
+    except Exception as e:
+        errors["cache"] = str(e)
+    if errors:
+        return JsonResponse({"status": "error", "errors": errors}, status=503)
+    return JsonResponse({"status": "ok"})