feat: unified Bubbletea progress UI for sync command

[jung-thomas]

Summary

• Replaces silent sync phases with a unified Bubbletea inline progress display showing a phase status list and animated progress bar throughout the entire sap-devs sync lifecycle
• Adds non-TTY fallback with plain text progress lines for CI, pipes, and inject --sync
• Integrates marker expansion sub-items as indented rows under the markers phase, removing the standalone Bubbletea program

Design

• Single syncModel in internal/ui/sync_progress.go with hand-rolled spinner + progress bar (no bubbles dependency)
• SAP Fiori Horizon Evening color palette via local lipgloss v1 constants
• cmd/sync.go refactored: buildSyncPlan pre-checks staleness → syncWorker goroutine sends typed messages → Bubbletea renders inline
• TTY detection gates Bubbletea vs PrintPlainProgress fallback
• "Up to date" fast path when all phases are fresh (no Bubbletea launched)

Test plan

• go build ./... && go vet ./... passes clean
• 12 unit tests for syncModel transitions and view rendering
• sync --force shows all phases with ✓/✗ status
• sync --force | cat produces clean plain text (no ANSI artifacts)
• sync --force --category events shows only archive block + events phase
• sync (after fresh sync) prints "up to date" with no progress bar