fix(data): guard against empty STORAGE_PATH and fix ADR markdown lint (#459)

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: nanotaboada

adr/0003-use-sqlite-for-data-storage.md

@@ -19,6 +19,7 @@ We will use SQLite as the database engine, accessed through Entity Framework Cor
 ## Consequences
 
 ### Positive
+
 - Zero-config: no server process, no connection string credentials, no Docker service dependency for local development.
 - EF Core abstracts the SQL dialect, so migrating to another database requires changing only the provider registration.
 - `MigrateAsync()` at startup ensures the schema is always up to date, making onboarding instant without committing binary database files.

src/Dotnet.Samples.AspNetCore.WebApi/Extensions/ServiceCollectionExtensions.cs

@@ -31,9 +31,10 @@ IWebHostEnvironment environment
     {
         services.AddDbContextPool<PlayerDbContext>(options =>
         {
-            var dataSource =
-                Environment.GetEnvironmentVariable("STORAGE_PATH")
-                ?? Path.Combine(AppContext.BaseDirectory, "storage", "players-sqlite3.db");
+            var storagePath = Environment.GetEnvironmentVariable("STORAGE_PATH");
+            var dataSource = !string.IsNullOrWhiteSpace(storagePath)
+                ? storagePath
+                : Path.Combine(AppContext.BaseDirectory, "storage", "players-sqlite3.db");
 
             var storageDir = Path.GetDirectoryName(dataSource);
             if (!string.IsNullOrWhiteSpace(storageDir))