Fix QuantizedGraph<float> source compatibility for v0.3.6

[gouyt13]

Problem and change

PR #105 made QuantizedGraph a non-template class, so existing C++ callers using QuantizedGraph<float> stopped compiling. Restore the float specialization while retaining the compiled implementation and C++17 deduction guides for callers that omit <float>.

Update the builder, Python bindings, examples, and documentation to use the restored API. Add regression coverage for explicit/default template arguments, deduction, and move semantics. Bump the CMake and Python package versions to 0.3.6.

Validation

• The original failing C++17 consumer now compiles, links, and runs.
• Release build with RABITQ_ENABLE_NATIVE_OPTIMIZATION=OFF: all 144 C++ tests passed; C++ samples built. Used the locally available GoogleTest 1.11.0.
• Rebuilt and installed the compatibility fix in the existing project environment: all 148 Python tests passed. Verified the imported extension contains QuantizedGraph<float>::search.
• C++ formatting, Python lint/formatting, focused clang-tidy, strict MkDocs build, and staged diff whitespace checks passed.
• Static analysis was focused; full clang-tidy remains a pre-merge check.

Compatibility

Restores the QuantizedGraph<float> C++ source API and preserves C++17 variable declarations using deduction. The implementation remains float-only. No index-format, Python API, or production dependency changes.