feat(i18n): add i18n infrastructure + Simplified Chinese, localize Settings screen (refs #68) (#97)

- Add expo-localization, i18next, react-i18next (versions aligned with
  Expo 54 / RN 0.81)
- src/lib/i18n/locale-resolve.ts: pure locale-resolution helpers
  (system tag -> supported catalog, with en fallback), unit-tested via
  node --test with no RN imports
- src/lib/i18n/config.ts: i18next init wired to expo-localization
  device detection, en.json + zh-Hans.json catalogs
- Persist a locale preference (system | en | zh-Hans) in the settings
  zustand store, applied immediately via i18next.changeLanguage
- Wire I18nextProvider in app/_layout.tsx
- Localize the Settings screen (~28 strings) as the reference pattern
  for extracting user-facing strings, with a language picker row and
  reviewed Simplified Chinese translations

Other screens (session/[id], connection/*, index, chat components)
are deferred follow-up — issue #68 stays open for that work.

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

package-lock.json

@@ -22,14 +22,17 @@
         "expo-image-picker": "17.0.10",
         "expo-linking": "~8.0.11",
         "expo-local-authentication": "~17.0.8",
+        "expo-localization": "~17.0.9",
         "expo-notifications": "~0.32.16",
         "expo-router": "~6.0.22",
         "expo-secure-store": "~15.0.8",
         "expo-speech-recognition": "3.0.1",
         "expo-status-bar": "~3.0.9",
         "expo-store-review": "~9.0.9",
+        "i18next": "^26.3.6",
         "posthog-react-native": "^4.57.0",
         "react": "19.1.0",
+        "react-i18next": "^17.0.10",
         "react-native": "0.81.5",
         "react-native-gesture-handler": "~2.28.0",
         "react-native-marked": "8.0.0",
@@ -4921,6 +4924,19 @@
         "expo": "*"
       }
     },
+    "node_modules/expo-localization": {
+      "version": "17.0.9",
+      "resolved": "https://registry.npmjs.org/expo-localization/-/expo-localization-17.0.9.tgz",
+      "integrity": "sha512-k5eYHr7iLMob3M8cHH6bgDrDRmqnZG8xKGLhpx8ST+LsFXmSgYpJ/t0VwWm0gz64C/K669XhObdG3D6QwCGqhw==",
+      "license": "MIT",
+      "dependencies": {
+        "rtl-detect": "^1.0.2"
+      },
+      "peerDependencies": {
+        "expo": "*",
+        "react": "*"
+      }
+    },
     "node_modules/expo-modules-autolinking": {
       "version": "3.0.25",
       "resolved": "https://registry.npmjs.org/expo-modules-autolinking/-/expo-modules-autolinking-3.0.25.tgz",
@@ -6043,6 +6059,15 @@
       ],
       "license": "MIT"
     },
+    "node_modules/html-parse-stringify": {
+      "version": "3.0.1",
+      "resolved": "https://registry.npmjs.org/html-parse-stringify/-/html-parse-stringify-3.0.1.tgz",
+      "integrity": "sha512-KknJ50kTInJ7qIScF3jeaFRpMpE8/lfiTdzf/twXyPBLAGrLRTmkz3AdTnKeh40X8k9L2fdYwEp/42WGXIRGcg==",
+      "license": "MIT",
+      "dependencies": {
+        "void-elements": "3.1.0"
+      }
+    },
     "node_modules/http-errors": {
       "version": "2.0.1",
       "resolved": "https://registry.npmjs.org/http-errors/-/http-errors-2.0.1.tgz",
@@ -6085,6 +6110,34 @@
         "node": ">= 14"
       }
     },
+    "node_modules/i18next": {
+      "version": "26.3.6",
+      "resolved": "https://registry.npmjs.org/i18next/-/i18next-26.3.6.tgz",
+      "integrity": "sha512-Bu5Z2nAXgfVyM8xvW3jk9EKRIuX37PudsrBViThNFx7CR7aaYTpP01cxNB/E4c4UUzTDiAZRstEhsRfPOL/8xA==",
+      "funding": [
+        {
+          "type": "individual",
+          "url": "https://www.locize.com/i18next"
+        },
+        {
+          "type": "individual",
+          "url": "https://www.i18next.com/how-to/faq#i18next-is-awesome.-how-can-i-support-the-project"
+        },
+        {
+          "type": "individual",
+          "url": "https://www.locize.com"
+        }
+      ],
+      "license": "MIT",
+      "peerDependencies": {
+        "typescript": "^5 || ^6 || ^7"
+      },
+      "peerDependenciesMeta": {
+        "typescript": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/ieee754": {
       "version": "1.2.1",
       "resolved": "https://registry.npmjs.org/ieee754/-/ieee754-1.2.1.tgz",
@@ -8347,6 +8400,33 @@
         "react": ">=17.0.0"
       }
     },
+    "node_modules/react-i18next": {
+      "version": "17.0.10",
+      "resolved": "https://registry.npmjs.org/react-i18next/-/react-i18next-17.0.10.tgz",
+      "integrity": "sha512-XneHftyYA774MJkkccSkZ5oKrUpCnXIPmxio3wemqrVzCRLWiGXOMbIzObrer03fNDEnm8g8R5yYls4HcE+esg==",
+      "license": "MIT",
+      "dependencies": {
+        "@babel/runtime": "^7.29.2",
+        "html-parse-stringify": "^3.0.1",
+        "use-sync-external-store": "^1.6.0"
+      },
+      "peerDependencies": {
+        "i18next": ">= 26.2.0",
+        "react": ">= 16.8.0",
+        "typescript": "^5 || ^6 || ^7"
+      },
+      "peerDependenciesMeta": {
+        "react-dom": {
+          "optional": true
+        },
+        "react-native": {
+          "optional": true
+        },
+        "typescript": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/react-is": {
       "version": "19.2.6",
       "resolved": "https://registry.npmjs.org/react-is/-/react-is-19.2.6.tgz",
@@ -8979,6 +9059,12 @@
         "node": "*"
       }
     },
+    "node_modules/rtl-detect": {
+      "version": "1.1.2",
+      "resolved": "https://registry.npmjs.org/rtl-detect/-/rtl-detect-1.1.2.tgz",
+      "integrity": "sha512-PGMBq03+TTG/p/cRB7HCLKJ1MgDIi07+QU1faSjiYRfmY5UsAttV9Hs08jDAHVwcOwmVLcSJkpwyfXszVjWfIQ==",
+      "license": "BSD-3-Clause"
+    },
     "node_modules/safe-buffer": {
       "version": "5.2.1",
       "resolved": "https://registry.npmjs.org/safe-buffer/-/safe-buffer-5.2.1.tgz",
@@ -10200,6 +10286,15 @@
       "integrity": "sha512-gQpnTgkubC6hQgdIcRdYGDSDc+SaujOdyesZQMv6JlfQee/9Mp0Qhnys6WxDWvQnL5WZdT7o2Ul187aSt0Rq+w==",
       "license": "MIT"
     },
+    "node_modules/void-elements": {
+      "version": "3.1.0",
+      "resolved": "https://registry.npmjs.org/void-elements/-/void-elements-3.1.0.tgz",
+      "integrity": "sha512-Dhxzh5HZuiHQhbvTW9AMetFfBHDMYpo23Uo9btPXgdYP+3T5S+p+jgNy7spra+veYhBP2dCSgxR/i2Y02h5/6w==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=0.10.0"
+      }
+    },
     "node_modules/walker": {
       "version": "1.0.8",
       "resolved": "https://registry.npmjs.org/walker/-/walker-1.0.8.tgz",