CIMNotebook: Connection Management & SecretStorage

[spah-soptim]

Objective: Utilize named connections via opencgmes.jsonc and securely store passwords.

Description:
Allow users to replace hardcoded URLs in markdown cells with named profiles.

• Extend validation.schema.json with a new top-level cimnotebook block.
• Backend: Implement NotebookConfig Jackson parsing for the JSONC file and a new listConnections LSP command.
• Frontend: Cache connections and implement the resolution hierarchy (Cell -> Workspace Default -> Config Default -> Error).
• Store authType: basic passwords securely in VS Code SecretStorage.
• Implement the Notebook StatusBar (registerNotebookCellStatusBarItemProvider) with QuickPick commands for fast target switching.

Acceptance Criteria:

• Endpoints can be set via the status bar (QuickPick) for the cell or workspace.
• Passwords never appear in plaintext in opencgmes.jsonc or Git; they are exclusively in VS Code SecretStorage.
• Passwords are never returned in the LSP channel (listConnections).
• Documentation includes trace-logging security risks regarding credentials.