feat(deploy): consolidated dev stack with auto-provisioned Zitadel

Single docker-compose stack for local development (Postgres, Zitadel,
RabbitMQ, SeaweedFS + bucket init, Jaeger) plus an optional overlay to run
the .NET apps in Docker. up.ps1 orchestrates the full bootstrap: stack up,
stream-ticket keys, EF Core migrations and Zitadel provisioning.

- Zitadel is provisioned automatically (service-account PAT -> project +
  OIDC app with JWT access token); the generated ClientId is wired into
  Musify.Api user-secrets and .env. No manual console steps.
- ZITADEL_EXTERNAL_DOMAIN=host.docker.internal so token validation works
  both with local apps and full-docker.
- App Dockerfiles copy AppSettings*.json to lowercase so config loads on
  case-sensitive Linux; Worker image ships ffmpeg.
- Scripts split by responsibility (common/stream-keys/migrate/provision);
  apps overlay de-duped via YAML anchors.
- Remove the superseded standalone seaweedfs compose; point docs/development
  at the unified stack.

backend/.dockerignore

@@ -0,0 +1,10 @@
+**/bin/
+**/obj/
+**/.vs/
+**/.idea/
+.git/
+.github/
+.agents/
+.claude/
+**/DesignSettings.json
+*.user

backend/Musify.Api.Dockerfile

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+# Build context: backend/  (docker compose -f deploy/docker-compose.apps.yml build)
+FROM mcr.microsoft.com/dotnet/sdk:10.0 AS build
+WORKDIR /src
+
+# Restore: copy central config + csproj files first to cache the layer.
+COPY Directory.Build.props Directory.Packages.props nuget.config ./
+COPY Musify.Domain/Musify.Domain.csproj                 Musify.Domain/
+COPY Musify.Application/Musify.Application.csproj        Musify.Application/
+COPY Musify.Infrastructure/Musify.Infrastructure.csproj Musify.Infrastructure/
+COPY Musify.Api/Musify.Api.csproj                        Musify.Api/
+RUN dotnet restore Musify.Api/Musify.Api.csproj
+
+COPY . .
+RUN dotnet publish Musify.Api/Musify.Api.csproj -c Release -o /app --no-restore
+# Config files are AppSettings*.json (PascalCase); on case-sensitive Linux the host
+# looks for appsettings*.json. Add lowercase copies so they get loaded.
+RUN cp /app/AppSettings.json /app/appsettings.json \
+    && cp /app/AppSettings.Development.json /app/appsettings.Development.json
+
+FROM mcr.microsoft.com/dotnet/aspnet:10.0 AS runtime
+WORKDIR /app
+COPY --from=build /app ./
+ENV ASPNETCORE_URLS=http://+:5111
+EXPOSE 5111
+ENTRYPOINT ["dotnet", "Musify.Api.dll"]

backend/Musify.StreamingGateway.Dockerfile

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+# Build context: backend/
+FROM mcr.microsoft.com/dotnet/sdk:10.0 AS build
+WORKDIR /src
+
+COPY Directory.Build.props Directory.Packages.props nuget.config ./
+COPY Musify.StreamingGateway/Musify.StreamingGateway.csproj Musify.StreamingGateway/
+RUN dotnet restore Musify.StreamingGateway/Musify.StreamingGateway.csproj
+
+COPY . .
+RUN dotnet publish Musify.StreamingGateway/Musify.StreamingGateway.csproj -c Release -o /app --no-restore
+
+FROM mcr.microsoft.com/dotnet/aspnet:10.0 AS runtime
+WORKDIR /app
+COPY --from=build /app ./
+ENV ASPNETCORE_URLS=http://+:8081
+EXPOSE 8081
+ENTRYPOINT ["dotnet", "Musify.StreamingGateway.dll"]

backend/Musify.Worker.Dockerfile

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+# Build context: backend/
+FROM mcr.microsoft.com/dotnet/sdk:10.0 AS build
+WORKDIR /src
+
+COPY Directory.Build.props Directory.Packages.props nuget.config ./
+COPY Musify.Domain/Musify.Domain.csproj                 Musify.Domain/
+COPY Musify.Application/Musify.Application.csproj        Musify.Application/
+COPY Musify.Infrastructure/Musify.Infrastructure.csproj Musify.Infrastructure/
+COPY Musify.Worker/Musify.Worker.csproj                 Musify.Worker/
+RUN dotnet restore Musify.Worker/Musify.Worker.csproj
+
+COPY . .
+RUN dotnet publish Musify.Worker/Musify.Worker.csproj -c Release -o /app --no-restore
+# AppSettings*.json (PascalCase) -> lowercase copies for case-sensitive Linux.
+RUN cp /app/AppSettings.json /app/appsettings.json \
+    && cp /app/AppSettings.Development.json /app/appsettings.Development.json
+
+FROM mcr.microsoft.com/dotnet/aspnet:10.0 AS runtime
+WORKDIR /app
+# ffmpeg: the Worker transcodes audio to .m4a.
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends ffmpeg \
+    && rm -rf /var/lib/apt/lists/*
+COPY --from=build /app ./
+ENTRYPOINT ["dotnet", "Musify.Worker.dll"]