Update docs for microservices architecture

DorkNet.Server/Data/MIGRATIONS.md

@@ -6,8 +6,9 @@
   (generated by `dotnet ef migrations add Initial` against the
   current entity model — captures all 67 `DbSet<>` tables).
 - **`LegacyUpgrades.cs`** holds idempotent data transforms that can't
-  be derived from the entity model. Runs once per server boot, after
-  EF migrations complete and before `RoomService.SeedAsync()`.
+  be derived from the entity model. Runs during host boot for the
+  standalone server and for service-slice containers, after schema
+  bootstrap completes and before `RoomService.SeedAsync()`.
 
 ## What changed in the consolidation
 
@@ -37,8 +38,8 @@ Both were collapsed in 2026-05-25:
 ## Production cutover (one-time SQL)
 
 Existing prod databases need a one-time fixup to tell EF "the new
-Initial is already applied here" so the next boot doesn't try to
-`CREATE TABLE` over existing data.
+Initial is already applied here" so the next standalone or service-slice
+boot doesn't try to `CREATE TABLE` over existing data.
 
 ### Postgres path
 
@@ -48,7 +49,7 @@ table exists** because EF Core only creates it when `Migrate()` runs.
 Postgres continues to use `EnsureCreated()` post-consolidation, so
 there's *nothing to do* — `EnsureCreated()` reads the entity model,
 sees the schema already matches, and no-ops. Just deploy the new
-build.
+standalone image or microservices compose stack.
 
 If you ever switch the Postgres path to `Migrate()`, run this once
 before the cutover deploy: