Embed the Composio key in the app bundle instead of shipping cred.txt

Root cause of the recurring 401: a revoked key was hardcoded in
startup-recovery.ts and onboarding-service.ts and reseeded into
composio_settings on every launch, and the interim fix shipped cred.txt
as a visible file under resources/.

- electron.vite.config.ts reads the gitignored cred.txt at build time
  and injects the key into the main-process bundle as
  __COMPOSIO_API_KEY__; no credential file is packaged and the key is
  not user-visible or configurable. The renderer bundle never sees it.
- Delete both hardcoded-key seeders; migration 046 purges stored
  api_key and never-read toolkits rows while keeping entity_id and
  auth_config state.
- Stop shipping composio_settings in the renderer snapshot.

src/shared/snapshot-domain.ts

@@ -140,14 +140,6 @@ export interface AppSnapshot {
   automationRules: AutomationRuleRecord[];
   meetings: MeetingRecord[];
   sprints: SprintRecord[];
-  composioSettings: ComposioSettingRecord[];
   connectorAccounts: ConnectorAccountRecord[];
   connectorGrants: ConnectorGrantRecord[];
 }
-
-export interface ComposioSettingRecord {
-  orgId: string;
-  key: string;
-  value: string;
-  updatedAt: string;
-}