Add DummySettings and DummyVectorStore for easier local testing

[Keerthipati-Harshith-Varma]

This PR introduces mock classes for standalone testing of the embedding pipeline without requiring full project dependencies.

Changes Made:
Added DummySettings and DummyVectorStore inside embedding_pipeline.py
Allows running the script independently for testing embeddings

Steps to Test:
Run the file using sample text input.
Confirm that add_texts and save_local run without dependency errors.

UI changes:
N/A

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