examples: migrate to the native data layer (drop ws/coder-websocket/jackson/jsonlite) (#316)

Stacked on #315 (the native Binance REST fetcher). Retarget to `main` once #315 merges.

Migrates the runnable examples off third-party data-I/O packages onto Wickra's
native data layer (`CandleReader`, `Resampler`, `BinanceFeed`, `fetch_*klines`).

## Third-party packages removed (the zero-dep selling point)
- **Node**: `ws` (live feed → BinanceFeed) — dropped from package.json + lockfile
- **Go**: `github.com/coder/websocket` — dropped from go.mod / go.sum (`go mod tidy`)
- **Java**: `jackson-databind` (live feed + REST fetch) — dropped from pom.xml
- **R**: `jsonlite` + `websocket` + `later` — dropped from the README notes

Each language's CSV loading now goes through `CandleReader`, manual resampling
through `Resampler`, the live feed through `BinanceFeed`, and (Java/R) the REST
download through the native fetcher.

## Verification
Ran the offline examples per language against the bundled data — backtest and
multi_timeframe produce identical output across Python / Node / Go / Java / R
(e.g. ATR(14) last 345.1010; 1h→5m resamples to 240 bars, →15m to 80 bars).

C# / C / WASM (stdlib-only, no third-party deps to remove) follow in this branch.

Note: the streaming `strategy_*` examples have pre-existing candle-indicator
runtime bugs (CI only syntax-smokes them); the CSV migration preserves their
shape and leaves those bugs for a separate fix.

examples/node/package-lock.json

@@ -10,9 +10,6 @@
       "license": "SEE LICENSE IN ../../LICENSE",
       "dependencies": {
         "wickra": "file:../../bindings/node"
-      },
-      "devDependencies": {
-        "ws": "^8.18.0"
       }
     },
     "../../bindings/node": {
@@ -23,7 +20,7 @@
         "@napi-rs/cli": "^2.18.0"
       },
       "engines": {
-        "node": ">= 18"
+        "node": ">= 20"
       },
       "optionalDependencies": {
         "wickra-darwin-arm64": "0.9.2",
@@ -37,28 +34,6 @@
     "node_modules/wickra": {
       "resolved": "../../bindings/node",
       "link": true
-    },
-    "node_modules/ws": {
-      "version": "8.21.0",
-      "resolved": "https://registry.npmjs.org/ws/-/ws-8.21.0.tgz",
-      "integrity": "sha512-Vsp28b7DRcimFQvrqu2Wek3z1iYxDCWqHYB8Qsnk/S4RfaCQzPGPyBNuVjJV3cd6UiKtUtp6sNM77gWvzcCH+g==",
-      "dev": true,
-      "license": "MIT",
-      "engines": {
-        "node": ">=10.0.0"
-      },
-      "peerDependencies": {
-        "bufferutil": "^4.0.1",
-        "utf-8-validate": ">=5.0.2"
-      },
-      "peerDependenciesMeta": {
-        "bufferutil": {
-          "optional": true
-        },
-        "utf-8-validate": {
-          "optional": true
-        }
-      }
     }
   }
 }