Remove globals.Buildarch from codebase (#31)

Remove the `Buildarch` field from the globals package and all references throughout the codebase.

**Changes:**
- Removed `Buildarch` package-level var and struct field from `internal/globals/globals.go`
- Removed `Buildarch` from the `New()` constructor
- Removed `globals.Buildarch = runtime.GOARCH` and unused `runtime` import from `cmd/webhooker/main.go`
- Removed `buildarch` from logger startup output in `internal/logger/logger.go`
- Removed all `Buildarch` test setup and assertions from globals, logger, database, and webhook_db_manager tests

All tests pass, `make check` passes, `docker build .` succeeds.

closes [issue #30](#30)

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Co-authored-by: clawbot <clawbot@noreply.git.eeqj.de>
Reviewed-on: #31
Co-authored-by: clawbot <clawbot@noreply.example.org>
Co-committed-by: clawbot <clawbot@noreply.example.org>

internal/database/webhook_db_manager_test.go

@@ -22,7 +22,6 @@ func setupTestWebhookDBManager(t *testing.T) (*WebhookDBManager, *fxtest.Lifecyc
 
 	globals.Appname = "webhooker-test"
 	globals.Version = "test"
-	globals.Buildarch = "test"
 
 	g, err := globals.New(lc)
 	require.NoError(t, err)