feat: cursor navigation, key sounds, dictionary tooling, key security

Batch of in-progress app work from the working tree.

- feat(keyboard): CursorNavigation + CursorDragPad for caret movement;
  KeyboardSoundFeedback for system key click sounds
- feat(dictionary): DictionaryAliasGenerator + PersonalDictionaryEntrySheet;
  TranscriptPostProcessor quality gate; retire DictionaryLearner
- feat(ui): TabBarVisibility handling; drop PageHeaderRow /
  PageHeaderConfirmButton; refresh views and localizable strings
- fix(security): move the hardcoded DeepSeek key out of
  PreconfiguredKeys.swift into a gitignored PreconfiguredKeys.local.swift
  (seeded from .example by generate-xcodeproj.sh)
- docs(agents): add Conventional Commits versioning + bilingual changelog rules
- chore(gitignore): ignore PreconfiguredKeys.local.swift, .cache/, pycache

Custom language model / lexicon work stays on
feature/custom-language-model-asr. Changelog bullets added under
[Unreleased]; no version bump.

Scripts/generate-xcodeproj.sh

@@ -21,6 +21,20 @@ if [[ ! -f "$SIGNING_LOCAL" ]]; then
   echo "Edit DEVELOPMENT_TEAM there if you use a personal Apple Developer account."
 fi
 
+# Local-engine DeepSeek key (gitignored). XcodeGen compiles this file;
+# the example ships a placeholder so fresh clones build after copy.
+PRECONFIG_LOCAL="$ROOT/OSGKeyboardShared/Services/PreconfiguredKeys.local.swift"
+PRECONFIG_EXAMPLE="$ROOT/OSGKeyboardShared/Services/PreconfiguredKeys.local.swift.example"
+if [[ ! -f "$PRECONFIG_LOCAL" ]]; then
+  if [[ ! -f "$PRECONFIG_EXAMPLE" ]]; then
+    echo "error: missing $PRECONFIG_EXAMPLE" >&2
+    exit 1
+  fi
+  cp "$PRECONFIG_EXAMPLE" "$PRECONFIG_LOCAL"
+  echo "Created $PRECONFIG_LOCAL from PreconfiguredKeys.local.swift.example"
+  echo "Edit deepseek in that file before using the local engine's built-in polish."
+fi
+
 xcodegen generate
 
 if python3 - "$PBXPROJ" <<'PY'