Scaffold the Before-M1 repo skeleton

Stand up the modular-monolith skeleton per docs/V1_BUILD_PLAN.md: one .NET 10
solution with web + worker hosts sharing seven interface-bounded module projects,
PostgreSQL 17 + pgvector via EF Core 10, a React 19 + Vite SPA built into wwwroot,
and Docker Compose for one-command local dev. Skeleton only — no feature code.

Architecture
- One project per module (OrgBoard, Identity, Skills, Assembler, Governance,
  Memory, Integrations); each is its own assembly so non-public types (entities,
  DbContext) are invisible across modules at compile time.
- TeamUp.Bootstrap is the only library that references all modules; both hosts
  reference only Bootstrap. SharedKernel/Infrastructure never reference modules.
- IModule seam: Register(...) runs in both hosts; MapEndpoints(...) only in web.
- PlatformDbContext owns the pgvector extension + the seven module schemas
  (InitialPlatform migration); MigrationRunner applies it then any module context.
- One image, two roles selected by RUN_MODE at the Docker entrypoint.

Verified
- dotnet build green (nullable + warnings-as-errors).
- ArchitectureTests 8/8 — reflection-based boundary rules (no module -> module,
  -> Infrastructure, -> Bootstrap, or -> host references).
- IntegrationTests 10/10 — Testcontainers boots the host against real pgvector:
  migration applies, vector extension + 7 schemas exist, /health 200, every
  /api/<module>/ping 200, /openapi/v1.json served.
- client builds clean (Vite 6 — pinned for Node 22.3.0; Vite 8 needs Node >=22.12).

Packages and base images route through the Nexus mirror (mirror.soroushasadi.com),
reachable from Iran when nuget.org / Docker Hub / MCR are not. CI is intentionally
deferred to a later session.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/TeamUp.IntegrationTests/PostgresFixture.cs

@@ -0,0 +1,27 @@
+using Testcontainers.PostgreSql;
+using Xunit;
+
+namespace TeamUp.IntegrationTests;
+
+/// <summary>A throwaway Postgres 17 + pgvector container, shared across the integration tests.</summary>
+public sealed class PostgresFixture : IAsyncLifetime
+{
+    private readonly PostgreSqlContainer _container = new PostgreSqlBuilder()
+        .WithImage("pgvector/pgvector:pg17")
+        .WithDatabase("teamup")
+        .WithUsername("teamup")
+        .WithPassword("teamup")
+        .Build();
+
+    public string ConnectionString => _container.GetConnectionString();
+
+    public async ValueTask InitializeAsync() => await _container.StartAsync();
+
+    public async ValueTask DisposeAsync() => await _container.DisposeAsync();
+}
+
+[CollectionDefinition(Name)]
+public sealed class PostgresCollection : ICollectionFixture<PostgresFixture>
+{
+    public const string Name = "postgres";
+}