refactor: consolidate loading/error states and extract instance actions hook

Frontend:
- Create reusable DataStates components (LoadingState, ErrorState, EmptyState)
- Refactor 12 pages to use shared state components instead of inline JSX
- Extract useInstanceActions hook to eliminate session action duplication
- Update dashboard and sessions pages to use shared hook

OpenSpec:
- Archive completed mobile-app-usability change (44/44 tasks)
- Archive completed add-config-profiles change (15/15 tasks)

Quality: TypeScript check passes, production build succeeds

openspec/changes/archive/2026-05-25-mobile-app-usability/specs/session-lifecycle-ux/spec.md

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+## ADDED Requirements
+
+### Requirement: Mobile Session Interactions
+The system SHALL provide touch-optimized interactions for session management on mobile.
+
+#### Scenario: Session card actions on mobile
+- **GIVEN** a session card displayed on mobile
+- **WHEN** the user wants to perform an action
+- **THEN** primary actions (Open/Terminal) are visible as prominent buttons
+- **AND** secondary actions (Stop, Restart, Delete) are accessible through an action menu
+- **AND** all action buttons have minimum 44px touch targets
+
+#### Scenario: Session stop confirmation on mobile
+- **GIVEN** the user taps Stop on a running session
+- **THEN** a confirmation dialog appears optimized for mobile viewport
+- **AND** the dialog fits within 320px width
+- **AND** the dialog actions are stacked vertically with full-width buttons
+
+#### Scenario: Session creation on mobile
+- **GIVEN** the user initiates session creation on mobile
+- **THEN** the creation form stacks vertically
+- **AND** all fields have minimum 44px height
+- **AND** the form is scrollable within the viewport
+
+#### Scenario: Loading states on mobile
+- **GIVEN** an async session operation on mobile
+- **WHEN** the operation is in progress
+- **THEN** a loading indicator is displayed
+- **AND** interactive elements are disabled to prevent double-submission