TUI: add richer profile health summaries

[rmanibus]

Summary

• split the internal TUI health model into explicit reachability and repository state
• show a streamlined Health summary in the selected profile pane instead of multiple raw status rows
• surface the last in-session check result for the selected profile

Testing

• env GOCACHE=/tmp/cloudstic-gocache go test -count=1 ./internal/tui ./cmd/cloudstic ./internal/app
• env GOCACHE=/tmp/cloudstic-gocache GOLANGCI_LINT_CACHE=/tmp/cloudstic-golangci-lint golangci-lint run ./internal/tui ./cmd/cloudstic ./internal/app

Related: #217

[codecov]

Codecov Report

❌ Patch coverage is 57.29167% with 41 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
internal/tui/shell.go	34.00%	31 Missing and 2 partials ⚠️
internal/tui/dashboard.go	85.71%	5 Missing ⚠️
cmd/cloudstic/cmd_tui_activity.go	72.72%	3 Missing ⚠️

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