release(0.2.0): bump version from 0.1.5 to 0.2.0

This release carries the full post-audit work — 46 new indicators
(25 → 71), an eight-family taxonomy restructure, new bindings for
RollingVWAP, the WASM streaming-update parity, the pyo3/numpy CVE
fix, the SMA/Bollinger drift bound, the O(1) LinearRegression
refactor, the UlcerIndex deque and the PSAR is_ready/reset fixes
plus a refreshed example suite and wiki. The earlier 0.1.5 number
was never published; jumping straight to 0.2.0 is the cleaner signal
for the scope of the change.

Bumped:
- Cargo.toml workspace + wickra-core workspace-dep version
- bindings/python/pyproject.toml
- bindings/node/package.json + optionalDependencies (six platform pins)
- 6 x bindings/node/npm/<target>/package.json
- Cargo.lock regenerated
- CHANGELOG.md [0.2.0] header + compare-link
- docs/wiki/Home.md published-versions table
- docs/wiki/Quickstart-{Rust,Node,WASM}.md + Warmup-Periods.md
  version-pinned narrative lines

Verified locally:
- cargo fmt/clippy/test (628 passed, 0 failed)
- cargo deny check (no suppression)
- bindings/node node --test (92/92)
- bindings/python pytest (118/118)
- import wickra reports 0.2.0 with 72 indicator classes

bindings/node/package.json

@@ -1,6 +1,6 @@
 {
   "name": "wickra",
-  "version": "0.1.5",
+  "version": "0.2.0",
   "description": "Streaming-first technical indicators: incremental, fast, install-free. Node bindings powered by Rust.",
   "author": "kingchenc <kingchencp@gmail.com>",
   "main": "index.js",
@@ -47,12 +47,12 @@
     "node": ">= 18"
   },
   "optionalDependencies": {
-    "wickra-linux-x64-gnu": "0.1.5",
-    "wickra-linux-arm64-gnu": "0.1.5",
-    "wickra-darwin-x64": "0.1.5",
-    "wickra-darwin-arm64": "0.1.5",
-    "wickra-win32-x64-msvc": "0.1.5",
-    "wickra-win32-arm64-msvc": "0.1.5"
+    "wickra-linux-x64-gnu": "0.2.0",
+    "wickra-linux-arm64-gnu": "0.2.0",
+    "wickra-darwin-x64": "0.2.0",
+    "wickra-darwin-arm64": "0.2.0",
+    "wickra-win32-x64-msvc": "0.2.0",
+    "wickra-win32-arm64-msvc": "0.2.0"
   },
   "scripts": {
     "build": "napi build --platform --release",