F5: add PPO, DPO and Coppock Curve price oscillators

Completes the F5 family (Price oscillators) end to end:

- Rust core: ppo.rs (Percentage Price Oscillator — MACD as a percentage
  of the slow EMA), dpo.rs (Detrended Price Oscillator — shifted price
  minus its SMA), coppock.rs (Coppock Curve — WMA of two summed ROCs).
  Each with a full Indicator impl, runnable doctest and reference /
  constant-series / warmup / reset / batch==streaming / non-finite tests.
- Python: PyPpo / PyDpo / PyCoppock PyO3 classes + module registration
  + .pyi stubs (defaults PPO=(12,26), DPO=20, Coppock=(14,11,10)).
- Node: DpoNode via the scalar macro, explicit PpoNode and CoppockNode;
  index.d.ts and index.js updated.
- WASM: WasmDpo / WasmPpo / WasmCoppock via the scalar macro.
- Wiki: Indicator-Ppo/Dpo/Coppock.md plus rows in Indicators-Overview.md
  and entries in Home.md.

cargo fmt + clippy (core/wickra/data/wasm/node) clean; 300 core tests,
25 data tests and 42 doctests green.

crates/wickra-core/src/lib.rs

@@ -45,8 +45,8 @@ pub mod indicators;
 pub use error::{Error, Result};
 pub use indicators::{
     Adx, AdxOutput, Aroon, AroonOutput, Atr, AwesomeOscillator, BollingerBands, BollingerOutput,
-    Cci, Cmo, Dema, Donchian, DonchianOutput, Ema, Hma, Kama, Keltner, KeltnerOutput,
-    MacdIndicator, MacdOutput, Mfi, Mom, Obv, Pmo, Psar, Roc, RollingVwap, Rsi, Sma, Smma,
+    Cci, Cmo, Coppock, Dema, Donchian, DonchianOutput, Dpo, Ema, Hma, Kama, Keltner, KeltnerOutput,
+    MacdIndicator, MacdOutput, Mfi, Mom, Obv, Pmo, Ppo, Psar, Roc, RollingVwap, Rsi, Sma, Smma,
     StochRsi, Stochastic, StochasticOutput, Tema, Trima, Trix, Tsi, UltimateOscillator, Vwap, Vwma,
     WilliamsR, Wma, Zlema, T3,
 };