Add master catalogue search index with TF-IDF NN retrieval and keyword

[falah2001]

• Implemented TF-IDF–based master catalogue search using cosine nearest neighbours for fast and scalable product retrieval.
• Added per-category TF-IDF keyword extraction to identify high-signal terms that define each merchandise category.
• Introduced keyword coverage analysis to measure how broadly or narrowly a term captures products within categories.
• Implemented shared keyword detection across categories to identify non-specific or high-frequency terms affecting search precision.
• Designed the module as a configurable, command-line tool supporting both query search and keyword exploration modes for flexible analysis workflows.