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/indicators/mod.rs

@@ -11,8 +11,10 @@ mod awesome_oscillator;
 mod bollinger;
 mod cci;
 mod cmo;
+mod coppock;
 mod dema;
 mod donchian;
+mod dpo;
 mod ema;
 mod hma;
 mod kama;
@@ -22,6 +24,7 @@ mod mfi;
 mod mom;
 mod obv;
 mod pmo;
+mod ppo;
 mod psar;
 mod roc;
 mod rsi;
@@ -48,8 +51,10 @@ pub use awesome_oscillator::AwesomeOscillator;
 pub use bollinger::{BollingerBands, BollingerOutput};
 pub use cci::Cci;
 pub use cmo::Cmo;
+pub use coppock::Coppock;
 pub use dema::Dema;
 pub use donchian::{Donchian, DonchianOutput};
+pub use dpo::Dpo;
 pub use ema::Ema;
 pub use hma::Hma;
 pub use kama::Kama;
@@ -59,6 +64,7 @@ pub use mfi::Mfi;
 pub use mom::Mom;
 pub use obv::Obv;
 pub use pmo::Pmo;
+pub use ppo::Ppo;
 pub use psar::Psar;
 pub use roc::Roc;
 pub use rsi::Rsi;