fix(auth): login-flow provisioning — public login_url + session app passwords

Two fixes surfaced while testing Login Flow v2 provisioning behind a split
internal/external host (Docker: server↔Nextcloud over http://app, browser
over http://localhost:8080):

1. login_url pointed at the internal host. Nextcloud builds the login URL
   from the request host, so the browser-facing URL came back as
   http://app/login/v2/flow/... — unreachable from the user's browser. The
   poll endpoint was already rewritten to the internal host (correct, the
   server polls it); now LoginFlowV2Client also rewrites the login_url origin
   to settings.nextcloud_public_issuer_url when set (passed at all 5
   construction sites). When unset, behaviour is unchanged.

2. The app-password format guard rejected raw session tokens. core/
   getapppassword returns a long alphanumeric token, not the dashed 25-char
   Security-settings format, so the dashed-only regex 400'd the one-click
   opt-in handoff. Relax APP_PASSWORD_PATTERN to `^[a-zA-Z0-9-]{20,256}$`;
   the authoritative validation is still the BasicAuth check against Nextcloud.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/unit/test_login_flow.py

@@ -151,6 +151,43 @@ async def test_poll_expired(flow_client):
     assert result.app_password is None
 
 
+async def test_initiate_rewrites_login_url_to_public_host():
+    """When server↔Nextcloud uses an internal host, the browser-facing login
+    URL must be rewritten to the configured public host; the poll endpoint
+    stays on the internal host for server-side polling."""
+    client = LoginFlowV2Client(
+        nextcloud_host="http://app:80",  # internal Docker host
+        verify_ssl=False,
+        public_host="http://localhost:8080",  # browser-reachable
+    )
+    mock_response = _mock_response(
+        200,
+        {
+            # Nextcloud builds these from the request (internal) host.
+            "login": "http://app/login/v2/flow/tok123",
+            "poll": {
+                "endpoint": "http://app/login/v2/poll",
+                "token": "secret-poll-token",
+            },
+        },
+    )
+    mock_client = AsyncMock()
+    mock_client.post.return_value = mock_response
+    mock_client.__aenter__ = AsyncMock(return_value=mock_client)
+    mock_client.__aexit__ = AsyncMock(return_value=False)
+
+    with patch(
+        "nextcloud_mcp_server.auth.login_flow.nextcloud_httpx_client",
+        return_value=mock_client,
+    ):
+        result = await client.initiate()
+
+    # Browser-facing URL uses the public host...
+    assert result.login_url == "http://localhost:8080/login/v2/flow/tok123"
+    # ...while the poll endpoint stays on the internal host (server polls it).
+    assert result.poll_endpoint == "http://app:80/login/v2/poll"
+
+
 async def test_initiate_with_custom_user_agent(flow_client):
     """Test that custom user agent is passed in the request."""
     mock_response = _mock_response(

tests/unit/test_management_app_password_endpoints.py

@@ -180,6 +180,25 @@ async def test_provision_app_password_invalid_format():
     assert "Invalid app password format" in response.json()["error"]
 
 
+def test_app_password_pattern_accepts_dashed_and_raw_tokens():
+    """The format guard accepts both the dashed Security-settings format and
+    the raw token from the one-click ``core/getapppassword`` flow, and still
+    rejects short / illegal-character input."""
+    from nextcloud_mcp_server.api.passwords import APP_PASSWORD_PATTERN
+
+    # Dashed format a user copies from Security settings.
+    assert APP_PASSWORD_PATTERN.match("abcde-ABCDE-12345-fghij-67890")
+    # Raw 72-char token returned by core/getapppassword (one-click opt-in).
+    assert APP_PASSWORD_PATTERN.match(
+        "kZmgLDQnqQHUAxhRq4d2VssBfjsI0PaHbL4JySWtwJkzVgAf34c0sZshEjZjuj1PLbwrf83q"
+    )
+    # Still rejects obviously-bad input.
+    assert not APP_PASSWORD_PATTERN.match("short")
+    assert not APP_PASSWORD_PATTERN.match("invalid-password")  # < 20 chars
+    assert not APP_PASSWORD_PATTERN.match("has spaces not allowed in this token")
+    assert not APP_PASSWORD_PATTERN.match("contains/slash/" + "a" * 20)
+
+
 async def test_provision_app_password_success(temp_storage, mocker):
     """Test successful app password provisioning."""
     # Mock settings (imported locally in the function)