[HIGH] RAG embeddings entirely mocked

[Muneerali199]

generateONNXEmbeddings() always falls back to generateMockEmbeddings() which generates random vectors. Semantic search has zero meaning - 'What should I eat' and 'capital of France' equally relevant.\n\nFile: Frontend/src/services/EmbeddingService.js, lines ~162-176\nFix: Integrate real embedding model or use backend ChromaDB for RAG