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-add-config-profiles/specs/user-config/spec.md

@@ -0,0 +1,35 @@
+## ADDED Requirements
+
+### Requirement: Config Profile Settings Editor
+The system SHALL expose a settings interface for managing the authenticated user's config profiles.
+
+#### Scenario: Browse config profiles in settings
+- **GIVEN** an authenticated user
+- **WHEN** they open settings
+- **THEN** they can view their config profiles
+- **AND** see each profile's name, compatibility scope, default status, and included profiles
+
+#### Scenario: Edit profile content in settings
+- **GIVEN** an authenticated user editing a config profile
+- **WHEN** they update env vars, runtime hints, mounts, text files, or include order
+- **THEN** the settings UI saves those changes through the config profile API
+- **AND** validation errors are shown without losing the user's draft edits
+
+#### Scenario: Configure profile defaults in settings
+- **GIVEN** an authenticated user editing config profiles
+- **WHEN** they mark a profile as the default for a global, project, tool, or project+tool context
+- **THEN** subsequent launches for matching contexts preselect that profile according to default specificity
+
+### Requirement: Launch Profile Selection UI
+The system SHALL allow the authenticated user to select one compatible config profile or `None` when starting a session.
+
+#### Scenario: Preselect default compatible profile
+- **GIVEN** an authenticated user has a default compatible profile for a selected project and tool type
+- **WHEN** they open the start session form
+- **THEN** the form preselects that profile
+- **AND** also offers `None` as a selectable option
+
+#### Scenario: Select no profile
+- **GIVEN** an authenticated user starts a session
+- **WHEN** they choose `None` in the config profile selector
+- **THEN** the start request records no selected config profile