Setup wizard P2: per-plugin config schema + settings-first creds

- Plugin contract gains get_config_schema(); the plugins list API returns it.
  Employees plugin declares its directory-DB fields (host/name/user + password).
- employee_connection reads host/name/user settings-first (env fallback); the
  password stays env-only.
- Setup wizard Features step renders each enabled plugin's config: non-secret
  fields save to settings; secrets are never stored - the wizard emits .env
  lines to paste. Fixed the plugins-list data path (data.plugins).
- Settings PUT now upserts (creates the row on first write) so plugin-config
  keys can be saved without pre-seeding.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

shopdb/plugins/__init__.py

@@ -143,6 +143,10 @@ class PluginManager:
                     meta = temp.meta
                     state = self.registry.get(name)
 
+                    try:
+                        config_schema = temp.get_config_schema()
+                    except Exception:
+                        config_schema = []
                     available.append({
                         'name': meta.name,
                         'version': meta.version,
@@ -151,7 +155,8 @@ class PluginManager:
                         'dependencies': meta.dependencies,
                         'installed': state is not None,
                         'enabled': state.enabled if state else False,
-                        'installedat': state.installed_at if state else None
+                        'installedat': state.installed_at if state else None,
+                        'config_schema': config_schema,
                     })
                 except Exception as e:
                     logger.warning(f"Error inspecting plugin {name}: {e}")

shopdb/plugins/base.py

@@ -74,6 +74,22 @@ class BasePlugin(ABC):
         """Return dict of service name -> service class."""
         return {}
 
+    def get_config_schema(self) -> List[Dict]:
+        """Declare the config fields this plugin needs, for the setup wizard.
+
+        Each field is a dict:
+          key      - the Setting key (non-secret) it maps to
+          label    - human label
+          type     - 'text' | 'number' | 'password'
+          secret   - True for credentials; these are NOT stored in the DB, the
+                     wizard emits an .env line for the operator to paste instead
+          envvar   - (secret only) the .env variable name to emit
+          default  - optional default shown as a placeholder
+          help     - optional hint
+        Return [] (default) if the plugin needs no configuration.
+        """
+        return []
+
     def get_setting(self, key: str, default=None):
         """Read a plugin-scoped setting from the core Setting store.