python: drop the NumPy runtime dependency (zero third-party deps) (#317)

Makes the Python binding truly dependency-free (Task 5b). `pip install wickra` now pulls **zero** third-party packages, and `import wickra` never imports NumPy (verified: `"numpy" not in sys.modules` after a batch call).

## What changed
- **Inputs** accept any sequence or buffer of numbers — `array.array`, `memoryview`, a NumPy `ndarray`, or a plain `list` — via `Vec` extraction (newtypes `Buf1`/`BufI64`). `PyBuffer` is unavailable under `abi3-py39`, and `unsafe_code = forbid` rules out a zero-copy slice, so inputs are copied once (negligible vs. compute).
- **Single-output `batch(...)`** returns a stdlib `array.array('d')` (native buffer protocol → `numpy.asarray` zero-copy).
- **Multi-output `batch(...)`** returns a buffer-protocol `Matrix` preserving `.shape`, integer-row and `[i, j]` access, and `.tolist()`.
- **NumPy** moves to an optional extra (`pip install wickra[numpy]`); it is never required.
- Streaming `update(...)` is unchanged; results are numerically identical.

## Implementation
- Trait `IntoPyData` + a `matrix()`/`f64_array()` helper collapse the ~400 batch call sites; `array.array` is built via `bytemuck` (Zlib/MIT/Apache — `cargo deny check licenses` ok).
- Tests migrated to `array.array`/`Matrix` (1-D `.shape`→`len()`, `.dtype`→`.typecode`; numeric comparisons normalize through a `_to_np` helper). The non-contiguous-input test now asserts acceptance instead of rejection.

## Verification (local)
- `pytest bindings/python/tests` — **1991 passed**.
- `cargo fmt --all`, `cargo clippy --workspace --all-targets --all-features -- -D warnings`, `cargo test --workspace --all-features`, `cargo deny check licenses` — all green.

**BREAKING for Python**: batch return types change from NumPy arrays to `array.array`/`Matrix`. Documented in CHANGELOG; ships with the data-layer release bundle (no separate tag).

CHANGELOG.md

@@ -7,6 +7,22 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+- **Python: zero third-party dependencies — NumPy is no longer required**
+  (breaking). `pip install wickra` now pulls nothing else. Batch inputs accept any
+  sequence or buffer of numbers (`array.array`, `memoryview`, a NumPy array, or a
+  plain `list`); single-output `batch(...)` now returns a stdlib `array.array('d')`
+  and multi-output indicators return a buffer-protocol `Matrix` (with `.shape`,
+  integer-row and `[i, j]` element access, `.tolist()`) instead of 1-D / 2-D NumPy
+  arrays. Both expose the buffer protocol, so `numpy.asarray(result)` still wraps a
+  1-D result zero-copy when NumPy is installed — it is now an optional extra
+  (`pip install wickra[numpy]`). Streaming `update(...)` is unchanged, and results
+  are numerically identical. The other nine languages were already dependency-free.
+
+### Removed
+- **Python: `numpy` runtime dependency** (see *Changed*). NumPy moves to the
+  optional `numpy`/`test`/`bench` extras.
+
 ### Fixed
 - **Binance kline feed: add the missing `3d` and `1M` intervals.** The
   `live-binance` `Interval` enum was missing three-day (`3d`) and one-month (`1M`)