feat(family-13): add Ichimoku + Heikin-Ashi (#50)

Two new indicators in a brand-new "Ichimoku & alternative charts"
family:

- `Ichimoku` (Ichimoku Kinko Hyo): the full five-line cloud system
  (Tenkan-sen, Kijun-sen, Senkou Span A/B, Chikou Span). Classic
  (9, 26, 52, 26) defaults; configurable. Forward displacement is
  handled in an O(1) ring buffer so the visible Senkou A/B at bar n
  are the values computed at bar n-displacement.
- `HeikinAshi`: recursive candle smoothing transform emitting a
  four-field synthetic candle. Seeds ha_open from (open+close)/2 on
  the first bar.

Touchpoints: core + unit tests, mod.rs/lib.rs re-exports, Python +
Node + WASM bindings (multi-output via PyArray2 / interleaved Vec<f64>
/ Object+Float64Array), Python tests across smoke/new-indicators/
input-validation, Node parity tests, fuzz target (Candle), benches,
README family table + counter (71 -> 73, 8 -> 9 families), CHANGELOG.

Note: Renko, Kagi, and Point & Figure from the family-13 ideas list
are intentionally skipped. They are bar generators (the bar boundary
is defined by price moves, not by a fixed time interval) rather than
indicators that consume a candle stream, and belong in wickra-data
as candle/tick transforms alongside the existing tick-to-candle
aggregator and resampler.

crates/wickra-core/src/indicators/mod.rs

@@ -62,11 +62,13 @@ mod force_index;
 mod fractal_chaos_bands;
 mod frama;
 mod garman_klass;
+mod heikin_ashi;
 mod hilbert_dominant_cycle;
 mod hilo_activator;
 mod historical_volatility;
 mod hma;
 mod hurst_channel;
+mod ichimoku;
 mod inertia;
 mod instantaneous_trendline;
 mod inverse_fisher_transform;
@@ -226,11 +228,13 @@ pub use force_index::ForceIndex;
 pub use fractal_chaos_bands::{FractalChaosBands, FractalChaosBandsOutput};
 pub use frama::Frama;
 pub use garman_klass::GarmanKlassVolatility;
+pub use heikin_ashi::{HeikinAshi, HeikinAshiOutput};
 pub use hilbert_dominant_cycle::HilbertDominantCycle;
 pub use hilo_activator::HiLoActivator;
 pub use historical_volatility::HistoricalVolatility;
 pub use hma::Hma;
 pub use hurst_channel::{HurstChannel, HurstChannelOutput};
+pub use ichimoku::{Ichimoku, IchimokuOutput};
 pub use inertia::Inertia;
 pub use instantaneous_trendline::InstantaneousTrendline;
 pub use inverse_fisher_transform::InverseFisherTransform;