fix(integrations): resolve error display, notification bugs, and integration UX improvements
- Fix purple outline on CustomSelect/MultiSelect dropdowns by deriving glowColor from primaryColor when not explicitly provided (was hardcoded purple)
- Fix legal notification reminder count sending wrong value: reminderCount and excludeWeekends are now synced across all channels (shared frequency settings), and handleSave reads from the active channel instead of arbitrary firstConfigured
- Resolve orchestration error codes from response.data.message (e.g. ORCH_035) and display user-friendly French messages instead of raw error codes
- Handle N8N_064 (invalid Azure AD credentials) with clear error messages across all Teams OAuth flows (wizard, dashboard, legal, public tender)
- Make wizard language selection optional: removed required marker, added click-to-deselect, send null when no language chosen (agent responds in user's language)
- Remove weekly (hebdomadaire) notification frequency option from UI; map backend WEEKLY to quotidien for backward compatibility
- Improve Slack integration: fetch channels from Slack API after token validation, show dropdown selector instead of manual text input with fallback
- Add replicated Teams team/channel selectors in wizard for existing integrations
- Pre-select connected account in integration modal, auto-switch to config view when no existing accounts, show info banner for empty state
- Use Azure AD client ID as platformAccountId for Teams duplicate detection
- Unify integration error handling via getIntegrationManagementErrorMessage