fix: improve indexing progress bar UX with multi-phase tracking

[echobt]

Description

This PR improves the indexing progress bar UX by:

1. Using MultiProgress: Ensures progress bars for different phases (Reading, Embedding, Storing) don't overwrite each other.
2. Preserving Phase Status: Instead of clearing the bar, we now use finish_with_message to leave a permanent record of what happened in each phase.
3. Adding ETAs: Enabled ETA calculation for long-running phases (Embedding, Storing).
4. Improved Messaging: clearer status messages for each phase.

Changes

• Modified Indexer::index_directory to use indicatif::MultiProgress.
• Replaced finish_and_clear() with finish_with_message().
• Added steady tick to progress bars for smoother animation.

Testing

Verified locally by running vgrep index and observing the new progress bar behavior.