Use Starlette, uvicorn and websockets; rename Docker files to container ones

Serve neo4j-browser with Starlette and uvicorn (the optional browser extra)
instead of a hand-written HTTP server, and handle Bolt over WebSocket with the
websockets library's Sans-I/O protocol. Rename Dockerfile, .dockerignore and
docker/ to Containerfile, .containerignore and container/.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

peo/discovery.py

@@ -0,0 +1,24 @@
+# SPDX-FileCopyrightText: 2026 Bart Broere
+# SPDX-License-Identifier: GPL-3.0-or-later
+"""The Neo4j discovery document, served over HTTP on both the browser and the Bolt port."""
+
+import json
+import os
+
+from .backend import NEO4J_VERSION
+
+
+def discovery_document(headers, bolt_port) -> bytes:
+    """The JSON Neo4j serves at ``/`` so clients can find the Bolt endpoint."""
+    host = headers.get("host") or "localhost"
+    if host.startswith("["):  # IPv6 literal, e.g. [::1]:7474
+        host = host[:host.index("]") + 1]
+    else:
+        host = host.split(":", 1)[0]
+    port = os.environ.get("PEO_ADVERTISED_BOLT_PORT", str(bolt_port))
+    return json.dumps({
+        "bolt_routing": f"neo4j://{host}:{port}",
+        "bolt_direct": f"bolt://{host}:{port}",
+        "neo4j_version": NEO4J_VERSION,
+        "neo4j_edition": "community",
+    }).encode()