Add users, roles, and per-novel permissions

Introduces accounts (ASP.NET Identity + cookie auth), four global
roles (Admin/Writer/Editor/Reviewer), per-novel ownership and grants
via ProjectMember, and a service-API-key principal for the MCP server
and background import jobs. Enforcement lives in the application
services (not endpoint filters) so the embedded agent and MCP tools,
which call the same services directly, can't bypass it. Web client
gets a login page, session-aware routing, and a People section for
managing per-novel access.

Also includes prior in-flight changes from this branch (CLAUDE.md
compliance pass, dev-deploy docker-compose setup) that were
uncommitted when this feature work started.

.editorconfig

@@ -107,7 +107,7 @@ dotnet_style_qualification_for_event = false:warning
 [*.cs]
 csharp_using_directive_placement = outside_namespace:silent
 csharp_prefer_simple_using_statement = true:suggestion
-csharp_prefer_braces = true:silent
+csharp_prefer_braces = when_multiline:suggestion
 # File-scoped, matching every .cs file in this repository. The C#-specific key wins
 # over dotnet_style_namespace_declarations, so the two must agree or the setting
 # silently flips for C#.