feat: finish baseline architecture #106

Description

Wires the application's configuration system into the LLM and analysis pipeline, replacing the previously hardcoded API key and model values with user-managed settings persisted in localStorage.

Key changes:

• Settings UI – adds an API key input field to the Settings modal. Other settings were not added, a subsequent task to populate and style this modal to fit the application should be created in subsequent iteration.
• Config-driven LLM – LLMConnector now accepts a ConfigManager instead of a raw adapter, reconfigures itself reactively via the new subscribe/notify mechanism whenever the config changes
• Config-driven analysis – LLMAnalysisService reads analysis.profile and llm.model from config instead of using hardcoded values
• ConfigManager subscriptions – adds subscribe/unsubscribe support so services can react to config changes without polling
• Error differentiation – distinguishes "LLM not configured" (missing API key) from other runtime errors, surfacing a dedicated ErrorNotConfigured status in the status bar

Related Issues

#106 (closed)