fix: resolve repo-wide bug with missing HRM and Manufacturing tables in EF model

- Identified and fixed a critical issue where 36 tables existed in the EF model but were absent in the actual database.
- Root cause traced to a `.gitignore` rule that prevented migration files from being tracked, leading to discrepancies between the model snapshot and the database.
- Removed problematic entities from the snapshot, generated a migration to add the missing tables, and confirmed successful application.
- Reverted the `.gitignore` rule to ensure future migrations are tracked properly.
- No changes to existing tables, ensuring no collateral schema drift occurred.

.gitignore

@@ -31,8 +31,11 @@ Thumbs.db
 .idea/
 
 # ── Migrations ─────────────────────────────────────────────────────────
-# New EF Core migrations are not committed. Note the 4 migrations already in
-# Backend/ERPCore/Infra/Persistence/Migrations/ stay tracked — .gitignore does
-# not apply to tracked files — so edits to those still get committed as normal.
-# Untracking them too takes `git rm --cached`.
-**/Migrations/
+# Reverted 2026-07-31: excluding new EF Core migrations while
+# ErpDbContextModelSnapshot.cs stayed tracked meant every `dotnet ef
+# migrations add` after the initial 4 silently produced a migration git would
+# never see, while the (tracked) snapshot's changes committed normally —
+# so the snapshot kept claiming tables existed that no migration in git
+# history ever created them. Confirmed live: 25 HRM tables + 11 Manufacturing
+# tables were missing from the actual database for exactly this reason.
+# Migrations now stay tracked like any other source file — commit them.