fix: installation commands in documentation (#104)

Author: mcop1

doc/03_Getting_Started/01_Installation/03_Advanced_Installation_Topics/05_Env_Var_Definitions.md

@@ -180,6 +180,8 @@ final readonly class SolrEnvVarDefinition implements EnvVarDefinitionInterface
 Use `--env-definition` to inject additional definitions alongside those defined in the profile,
 without modifying the profile itself:
 
+> When running via Docker, prepend `docker compose exec php` to the command below.
+
 ```bash
 vendor/bin/pimcore-install \
   --install-profile='App\Installer\SkeletonProfile' \

doc/03_Getting_Started/01_Installation/03_Advanced_Installation_Topics/06_Post_Install_Commands.md

@@ -111,6 +111,8 @@ final class CustomDataMigration implements PostInstallHookInterface
 Use `--post-install-commands` to inject additional `PostInstallCommandsProviderInterface`
 implementations without modifying the profile:
 
+> When running via Docker, prepend `docker compose exec php` to the commands below.
+
 ```bash
 vendor/bin/pimcore-install \
   --install-profile='App\Installer\SkeletonProfile' \

doc/03_Getting_Started/01_Installation/03_Advanced_Installation_Topics/README.md

@@ -9,14 +9,25 @@ To fully automate the installation process, set all required values as environme
 and pass the `--no-interaction` flag:
 
 ```bash
-DATABASE_URL='mysql://pimcore:pimcore@db:3306/pimcore' \
-PIMCORE_ADMIN_USER=admin \
-PIMCORE_ADMIN_PASSWORD='secure-password' \
-docker compose exec php vendor/bin/pimcore-install \
-  --install-profile='App\Installer\SkeletonProfile' \
-  --no-interaction
+docker compose exec \
+  -e DATABASE_URL='mysql://pimcore:pimcore@db:3306/pimcore' \
+  -e PIMCORE_ADMIN_USER=admin \
+  -e PIMCORE_ADMIN_PASSWORD='secure-password' \
+  php vendor/bin/pimcore-install \
+    --install-profile='App\Installer\SkeletonProfile' \
+    --no-interaction
 ```
 
+:::info
+
+`docker compose exec` does not forward host-shell environment variables into the
+container automatically. Pass each variable explicitly with `-e VAR=value` (or
+`-e VAR` to forward a variable already exported in the host shell), or set the
+values in your `.env` / `docker-compose.yaml` so they are available to the `php`
+service at runtime.
+
+:::
+
 The `--no-interaction` flag suppresses all interactive prompts.
 All required values must be provided via environment variables or CLI options.
 
@@ -102,6 +113,8 @@ and the available extension points for developers:
 By default, the installer validates all collected values (e.g., testing the database connection,
 pinging OpenSearch). To skip validation during development:
 
+> When running via Docker, prepend `docker compose exec php` to the commands below.
+
 ```bash
 # Skip all validation
 vendor/bin/pimcore-install --install-profile='App\Installer\MyProfile' --skip-validation