Add resilient server-action UX: retries, offline hints, and consistent error toasts

[ganeshwhere]

Objective

Standardize resilient client UX for server-action failures.

Scope

• Retry path for transient failures
• Consistent loading/success/error feedback patterns
• Clear user-facing recovery messaging

Acceptance Criteria

• Mutation failures surface actionable feedback
• Retry action is available for transient failures
• No silent failures for team/project/task/chat actions
• Shared implementation pattern documented for future actions

Non-Goals

• Full offline queue synchronization