feat(scenarios): add step title, scenario credentials, and environment context in executor

- add nullable title column to scenario steps; exposed in create/edit forms and step table
- add scenario-credential join (many-to-many with CredentialEntity) with CRUD endpoints
- expose environment URLs in code executor helpers via helpers.env and helpers.getEnvUrl()
- resolve and cache environment per run from the login step's environmentName in scheduler
- add section spacing and step table title column to ScenarioDetailPage

client/src/i18n/locales/en.json

@@ -3,11 +3,13 @@
     "not_found": "Not found",
     "not_found_session": "Session {{id}} does not exist or has been deleted.",
     "not_found_environment": "Environment {{id}} does not exist or has been deleted.",
+    "not_found_credential": "Credential {{id}} does not exist or has been deleted.",
     "not_found_scenario": "Scenario {{id}} does not exist or has been deleted.",
     "generic": "Something went wrong. Please try again."
   },
   "nav": {
     "environments": "Environments",
+    "credentials": "Credentials",
     "keys": "Keys",
     "sessions": "Sessions",
     "scenarios": "Scenarios",
@@ -44,8 +46,32 @@
     "field_updated": "Updated",
     "section_urls": "URLs"
   },
+  "credentials": {
+    "title": "Credentials",
+    "empty": "No credentials yet.",
+    "loading": "Loading…",
+    "menu_label": "Credential options",
+    "action_edit": "Edit",
+    "action_delete": "Delete",
+    "action_add": "Add credential",
+    "action_save": "Create",
+    "action_update": "Save changes",
+    "action_cancel": "Cancel",
+    "create_title": "New Credential",
+    "edit_title": "Edit Credential",
+    "form_name": "Name",
+    "form_name_placeholder": "e.g. staging-api-key",
+    "form_name_required": "Name is required",
+    "form_data": "Data (JSON)",
+    "form_data_placeholder": "{\"token\": \"…\"}",
+    "form_data_invalid_json": "Must be valid JSON",
+    "field_id": "ID",
+    "field_last_used": "Last Used",
+    "field_created": "Created",
+    "field_updated": "Updated",
+    "section_data": "Data"
+  },
   "keys": {
-    "title": "Keys",
     "col_name": "Key name",
     "empty": "No key files found."
   },
@@ -81,6 +107,7 @@
     "field_updated": "Updated",
     "steps_heading": "Steps",
     "step_order": "#",
+    "step_title": "Title",
     "step_type": "Type",
     "step_session": "Session",
     "step_updated": "Updated",
@@ -94,7 +121,22 @@
     "edit_title": "Edit Scenario",
     "form_name": "Name",
     "form_name_placeholder": "e.g. Login flow",
-    "form_name_required": "Name is required"
+    "form_name_required": "Name is required",
+    "credentials_heading": "Credentials",
+    "cred_empty": "No credentials assigned.",
+    "cred_col_alias": "Alias",
+    "cred_col_name": "Credential",
+    "cred_col_added": "Added",
+    "cred_action_add": "Add credential",
+    "cred_action_remove": "Remove",
+    "cred_action_save": "Add",
+    "cred_action_cancel": "Cancel",
+    "cred_form_cred": "Credential",
+    "cred_form_cred_placeholder": "Select credential…",
+    "cred_form_cred_required": "Select a credential",
+    "cred_form_alias": "Alias",
+    "cred_form_alias_placeholder": "e.g. api_key",
+    "cred_form_alias_required": "Alias is required"
   },
   "theme": {
     "switch_to_light": "Switch to light theme",
@@ -121,6 +163,8 @@
     "action_cancel": "Cancel",
     "form_order": "Order",
     "form_order_invalid": "Order must be a non-negative integer",
+    "form_title": "Title",
+    "form_title_placeholder": "e.g. Check login page",
     "form_type": "Type",
     "form_session": "Session name",
     "form_session_placeholder": "e.g. my-session",