Add Redis Search API surface (FT.CREATE, FT.DROPINDEX, FT.SEARCH)

[viktoriya-kutsarova]

Add Redis Search API surface for FT.CREATE, FT.DROPINDEX, and FT.SEARCH

This PR introduces the public API types for Redis Search commands without the driver-specific implementations.

API Interface

RedisSearchCommands defines the core operations:

• createIndex(name, schema) / createIndex(name, schema, definition) - create an index with optional configuration
• dropIndex(name) / dropIndex(name, options) - drop an index with optional document deletion
• search(index, query) / search(index, query, options) - execute a search query

Index Definition

• IndexDefinition - index-level options (data type, prefixes, language, stopwords, etc.)
• IndexDataType - HASH or JSON
• Language - supported stemming languages
• DropIndexOptions - controls whether to delete documents on drop

Schema & Field Types

• Schema - container for field definitions
• SchemaField - abstract base with factory methods (text(), tag(), numeric(), geo())
• TextField - full-text with stemming, phonetics, weight
• TagField - exact-match with separator and case sensitivity
• NumericField / GeoField - range queries and sorting

Search

• SearchQuery - query string wrapper
• SearchOptions - LIMIT, SORTBY, RETURN, WITHSCORES, VERBATIM, etc.
• SearchResult / SearchHit / SearchDocument - result types

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