Add embedding and storage modules

[ParamThakkar123]

Summary

• Add src/embeddings.jl – embedding generation module with support for multiple backends (OpenAI, Gemini, HuggingFace)
• Add src/storage.jl – vector storage module for persisting and querying embeddings
• Add test/EmbeddingsTest.jl and test/StorageTest.jl – test suites for both modules
• Update src/HealthLLM.jl and src/database.jl – integrate new modules
• Update docs/src/embeddings.md – documentation for the embedding system
• Update docs/make.jl and docs/src/index.md – include new docs in build
• Update test/runtests.jl and test/Project.toml – register new tests

[codecov]

Codecov Report

❌ Patch coverage is 65.47884% with 155 lines in your changes missing coverage. Please review.
✅ Project coverage is 65.64%. Comparing base (8c40129) to head (578bf2d).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/storage.jl	49.38%	41 Missing ⚠️
src/ingestion/pipeline.jl	0.00%	30 Missing ⚠️
src/database.jl	38.46%	24 Missing ⚠️
src/ingestion/fetch.jl	51.06%	23 Missing ⚠️
src/embeddings.jl	70.90%	16 Missing ⚠️
src/ingestion/search.jl	11.11%	16 Missing ⚠️
src/ingestion/chunk.jl	97.00%	5 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main      #50       +/-   ##
===========================================
+ Coverage   27.27%   65.64%   +38.37%     
===========================================
  Files           4       12        +8     
  Lines          88      521      +433     
===========================================
+ Hits           24      342      +318     
- Misses         64      179      +115     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.