Fixes a number of compilation errors that occur when the "full" feature set is enabled

[logankoester]

A number of compile-time errors occur when the "full" feature set is enabled.

This change resolves each of these errors, allowing the examples to run as expected (eg: cargo run --example ollama_local --features full) and the test suite to pass (cargo test --features full).

Changes:

• Replaces malformed Ollama embeddings API call with GenerateEmbeddingsRequest::new() constructor pattern
• Fixes Ollama LLM temperature parameter type (f32) and FormatType::Json variant
• Fixes URL parsing in Ollama embedder to properly construct host string with scheme
• Updates OpenAI API calls to use ResponseFormat::JsonObject enum variant instead of unsupported struct initialization and changes message content from string references to owned strings
• Adds missing url crate dependency, pinned to version 2.5.8
• Eliminates compiler warnings for unused mutable variables in PostgreSQL implementation (where_clauses variables)
• Removes unused imports from Qdrant vector store implementation
• Updates Qdrant delete operation to use DeletePointsBuilder pattern instead of manual PointsSelector construction (which fails to compile due to incompatibility with the qdrant-client crate)
• Fixes an output formatting error in async OpenAI example