docs: include PostgreSQL information

Author: Diogo-Ferraz

README.md

@@ -17,7 +17,7 @@ flowchart LR
     SPA["TaskManagementClient (Angular SPA)"] -->|"HTTPS"| Caddy["Caddy Reverse Proxy"]
     Caddy -->|"HTTPS"| Auth["Auth Service<br/>OpenIddict + Identity"]
     Caddy -->|"HTTPS"| Api["API Service<br/>Projects + TaskItems + Activity"]
-    Auth --> Db[("SQL Server")]
+    Auth --> Db[("SQL Server / PostgreSQL")]
     Api --> Db
 ```
 
@@ -123,7 +123,7 @@ Benefits:
 ## Tech Stack
 
 - ASP.NET Core (.NET 8)
-- EF Core (SQL Server)
+- EF Core (SQL Server + PostgreSQL)
 - MediatR
 - FluentValidation
 - AutoMapper
@@ -151,6 +151,10 @@ Benefits:
 ### `SQL Server`
 - Shared persistence for Auth and API domains
 
+### `PostgreSQL`
+- Alternative shared persistence for Auth and API domains
+- Can run side-by-side with SQL Server during migration
+
 ### `Caddy`
 - Local HTTPS termination
 - Routing for `auth.localhost` and `api.localhost`
@@ -171,14 +175,25 @@ You can copy `.env.example` to `.env` and adjust values if needed.
 
 Database selection:
 - `DATABASE_PROVIDER=SqlServer` (default, current baseline)
-- `DATABASE_PROVIDER=Postgres` (PostgreSQL path during migration)
+- `DATABASE_PROVIDER=Postgres` (PostgreSQL runtime mode)
 
 ### Run
 ```bash
 docker compose up --build
 ```
 
-This starts SQL Server, Auth, API, and Caddy with local HTTPS routing.
+This starts SQL Server, PostgreSQL, Auth, API, and Caddy with local HTTPS routing.
+Only the provider selected by `DATABASE_PROVIDER` is used by Auth/API at runtime.
+
+Examples:
+
+```bash
+# default (SQL Server)
+DATABASE_PROVIDER=SqlServer docker compose up --build
+
+# PostgreSQL mode
+DATABASE_PROVIDER=Postgres docker compose up --build
+```
 
 ---