fix(android): working signed release APK

- docker/android.Dockerfile: install nodejs (image ships Bun; ci-android-sign.sh
  patches build.gradle with a Node script).
- buffer polyfill: whisper.rn -> safe-buffer requires Node's `buffer`, absent in
  Metro/RN. Add `buffer` dep, alias it in metro.config.js, set the global in
  _layout. Web export unaffected (verified).

Validated locally end-to-end: assembleRelease BUILD SUCCESSFUL, 117MB APK across
all 4 ABIs with librnwhisper.so, signed (CN=Wisp, O=briggen.dev).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

bun.lock

@@ -7,6 +7,7 @@
       "dependencies": {
         "@expo/ui": "~56.0.17",
         "@huggingface/transformers": "^4.2.0",
+        "buffer": "^6.0.3",
         "dexie": "^4.4.3",
         "expo": "~56.0.11",
         "expo-constants": "~56.0.18",
@@ -595,6 +596,8 @@
 
     "bser": ["bser@2.1.1", "", { "dependencies": { "node-int64": "^0.4.0" } }, "sha512-gQxTNE/GAfIIrmHLUE3oJyp5FO6HRBfhjnw4/wMmA63ZGDJnWBmgY/lyQBpnDUkGmAhbSe39tx2d/iTOAfglwQ=="],
 
+    "buffer": ["buffer@6.0.3", "", { "dependencies": { "base64-js": "^1.3.1", "ieee754": "^1.2.1" } }, "sha512-FTiCpNxtwiZZHEZbcbTIcZjERVICn9yq/pDFkTl95/AxzD1naBctN7YO68riM/gLSDY7sdrMby8hofADYuuqOA=="],
+
     "buffer-from": ["buffer-from@1.1.2", "", {}, "sha512-E+XQCRwSbaaiChtv6k6Dwgc+bx+Bs6vuKJHHl5kox/BaKbhiXzqQOwK4cO22yElGp2OCmjwVhT3HmxgyPGnJfQ=="],
 
     "bytes": ["bytes@3.1.2", "", {}, "sha512-/Nf7TyzTx6S3yRJObOAV7956r8cr2+Oj8AC5dt8wSP3BQAoeX58NoHyCU8P8zGkNXStjTSi6fzO6F0pBdcYbEg=="],
@@ -839,6 +842,8 @@
 
     "hyphenate-style-name": ["hyphenate-style-name@1.1.0", "", {}, "sha512-WDC/ui2VVRrz3jOVi+XtjqkDjiVjTtFaAGiW37k6b+ohyQ5wYDOGkvCZa8+H0nx3gyvv0+BST9xuOgIyGQ00gw=="],
 
+    "ieee754": ["ieee754@1.2.1", "", {}, "sha512-dcyqhDvX1C46lXZcVqCpK+FtMRQVdIMN6/Df5js2zouUsqG7I6sFxitIC+7KYK29KdXOLHdu9zL4sFnoVQnqaA=="],
+
     "ignore": ["ignore@5.3.2", "", {}, "sha512-hsBTNUqQTDwkWtcdYI2i06Y/nUBEsNEDJKjWdigLvegy8kDuJAS8uRlpkkcQpyEXL0Z/pjDy5HBmMjRCJ2gq+g=="],
 
     "image-size": ["image-size@1.2.1", "", { "dependencies": { "queue": "6.0.2" }, "bin": { "image-size": "bin/image-size.js" } }, "sha512-rH+46sQJ2dlwfjfhCyNx5thzrv+dtmBIhPHk0zgRUukHzZ/kRueTJXoYYsclBaKcSMBWuGbOFXtioLpzTb5euw=="],