perf(db): pool BaseDbContext registrations in Startup

Swap AddDbContext<BaseDbContext> to AddDbContextPool<BaseDbContext> in
all three mutually-exclusive host registration branches (primary
connection, fallback connection, localhost placeholder). Pool size is
left at the default (1024). BaseDbContext has a
DbContextOptions<BaseDbContext> ctor and no OnConfiguring override, so
pooling is semantically equivalent to the current scoped registration
from the caller's perspective.

This commit has no observable effect on its own because three plugins
(Workflow, TimePlanning, BackendConfiguration) still re-register
BaseDbContext via plain AddDbContext, and DI resolves last-wins. Those
re-registrations are removed in the next commit to actually engage
pooling.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: renemadsen

eFormAPI/eFormAPI.Web/Startup.cs

@@ -107,7 +107,7 @@ public void ConfigureServices(IServiceCollection services)
         {
             Log.LogEvent($"We do have a ConnectionString {Configuration["ConnectionString"]}");
             services.AddEntityFrameworkMySql()
-                .AddDbContext<BaseDbContext>(o => o.UseMySql(
+                .AddDbContextPool<BaseDbContext>(o => o.UseMySql(
                     Configuration["ConnectionString"], new MariaDbServerVersion(
                         ServerVersion.AutoDetect(Configuration["ConnectinString"])), mySqlOptionsAction: builder =>
                     {
@@ -159,7 +159,7 @@ public void ConfigureServices(IServiceCollection services)
                 {
                     Log.LogEvent($"ConnectionString is {Configuration.MyConnectionString()}");
                     services.AddEntityFrameworkMySql()
-                        .AddDbContext<BaseDbContext>(o => o.UseMySql(
+                        .AddDbContextPool<BaseDbContext>(o => o.UseMySql(
                             Configuration.MyConnectionString(), new MariaDbServerVersion(
                                 ServerVersion.AutoDetect(Configuration.MyConnectionString())), mySqlOptionsAction: builder =>
                             {
@@ -208,7 +208,7 @@ public void ConfigureServices(IServiceCollection services)
                     // We use this hack to get the project started and we actually don't use this connection, but it's needed for the service to start.
                     // Once we have the correct connectionstring in the connection.json, we restart the server and the above method is used.
                     services.AddEntityFrameworkMySql()
-                        .AddDbContext<BaseDbContext>(o => o.UseMySql(
+                        .AddDbContextPool<BaseDbContext>(o => o.UseMySql(
                             "server=localhost;", new MariaDbServerVersion(
                                 new Version(10, 4, 0)), mySqlOptionsAction: builder =>
                             {