feat: add native Bitcoin (SegWit) chain config

Adds a Bitcoin entry (assetId 0, type "bitcoinNative", precision 8) mirroring
Tron's chain-family shape: "bitcoinBased" + "noSubstrateRuntime" options, a
mempool.space REST API URL as the "node" (same role TronGrid's URL plays for
Tron), and mempool.space itself as the block explorer.

Adds gradient chain icon + colored token icon (orange #F7931A, built from
the existing white Bitcoin glyph already vendored from Nova, matching this
repo's established icon-construction pattern for every other coin).

Lands on pending/post-fix-release, not master - per the existing plan to
ship Tron and Bitcoin support together in one coordinated release once
wallet-android's corresponding send features are done.

chains/v17/android/chains.json

@@ -294,6 +294,49 @@
       "themeColor": "#EB0029"
     }
   },
+  {
+    "chainId": "bip122:000000000019d6689c085ae165831e93",
+    "name": "Bitcoin",
+    "icon": "https://raw.githubusercontent.com/pezkuwichain/pezkuwi-wallet-utils/master/icons/chains/gradient/Bitcoin.svg",
+    "addressPrefix": 0,
+    "options": [
+      "bitcoinBased",
+      "noSubstrateRuntime"
+    ],
+    "nodeSelectionStrategy": "roundRobin",
+    "nodes": [
+      {
+        "url": "https://mempool.space/api",
+        "name": "mempool.space"
+      }
+    ],
+    "explorers": [
+      {
+        "name": "mempool.space",
+        "extrinsic": "https://mempool.space/tx/{value}",
+        "account": "https://mempool.space/address/{value}"
+      }
+    ],
+    "externalApi": {},
+    "assets": [
+      {
+        "assetId": 0,
+        "symbol": "BTC",
+        "precision": 8,
+        "name": "Bitcoin",
+        "priceId": "bitcoin",
+        "staking": null,
+        "type": "bitcoinNative",
+        "icon": "https://raw.githubusercontent.com/pezkuwichain/pezkuwi-wallet-utils/master/icons/tokens/colored/BTC.svg",
+        "buyProviders": {},
+        "sellProviders": {},
+        "typeExtras": null
+      }
+    ],
+    "additional": {
+      "themeColor": "#F7931A"
+    }
+  },
   {
     "chainId": "91b171bb158e2d3848fa23a9f1c25182fb8e20313b2c1eb49219da7a70ce90c3",
     "name": "Polkadot",