Add state tracking to Sync Diagnostics Client

[bean1352]

App state (credentials, dynamic schema, client parameters, query history) now lives in a dedicated local PowerSync DB (localStateDb) instead of localStorage. No app state is stored in localStorage.

• Local DB schema - Three tables: query_history, app_settings (credentials + dynamic_schema), client_parameters.
• Two PowerSync databases - synced database (db) for backend data and dynamic schema; local-only database (localStateDb) for app state (credentials, schema cache, client params, query history). Default context uses db; components that need local state use a nested PowerSyncContext.Provider value={localStateDb} so useQuery/writes hit the correct database.
• Credentials - Stored in local DB (app_settings.powersync_credential).
• Dynamic schema - Persisted in app_settings.dynamic_schema. Debounced (150 ms) during sync; immediate on connect/clear.
• Sync overview - Added TanStack useQuery for cached stats (conditional queries + invalidation on DB change). PowerSync useQuery kept for simple reactive SQL elsewhere.
• SQL console - Added query history drop down.
• Rust client implementation - Removed the option to switch to the JavaScript implementation as the Rust implementation will soon be the default.
• Client Parameters - These are now automatically saved as you type, I think this is better UX.

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Latest commit: 941e802

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