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/tool-instances/spec.md

@@ -0,0 +1,22 @@
+## ADDED Requirements
+
+### Requirement: Mobile Instance Controls
+The system SHALL ensure instance control actions are usable on mobile viewports.
+
+#### Scenario: Control button visibility on mobile
+- **GIVEN** an instance card or detail view on mobile
+- **THEN** control buttons (Start, Stop, Restart, Delete) have minimum 44px height
+- **AND** buttons have adequate spacing between them
+- **AND** button labels are readable at mobile font sizes
+
+#### Scenario: Instance status display on mobile
+- **GIVEN** an instance on mobile
+- **THEN** the status indicator is clearly visible
+- **AND** status text does not wrap awkwardly
+- **AND** health/probe information is accessible without horizontal scrolling
+
+#### Scenario: Instance creation form on mobile
+- **GIVEN** the instance creation flow on mobile
+- **THEN** all configuration fields stack vertically
+- **AND** dropdowns and selects are usable with touch
+- **AND** the submit button is prominent and reachable