feat: Scaffold UI screens and update project specification

- Create stub files for all UI screens defined in the tech spec (InventoryList, ItemDetails, ItemEdit, LabelsList, LocationsList, Search).
- Add corresponding ViewModels for each new screen.
- Update `tech_spec/project_structure.txt` to include the new files and mark them as 'stub'.
- Update `tech_spec/tech_spec.txt` to reflect the current implementation status, changing feature statuses to 'in_progress'.
- Add the undocumented `SearchScreen` to the project specification.
- Add `*.hprof` files to `.gitignore` to exclude memory dumps from version control.

.gitignore

@@ -1,34 +1,2 @@
-# Gradle
-.gradle/
-build/
-!gradle/wrapper/gradle-wrapper.jar
-
-# Local configuration
-local.properties
-
-# IDE files
-.idea/
-*.iml
-*.ipr
-*.iws
-.DS_Store
-
-# Keystore files
-*.jks
-*.keystore
-
-# Google Services
-app/google-services.json
-
-# Captures
-captures/
-*.apk
-*.aab
-output.json
-
-# Log files
-*.log
-
-# Gemini files
-GEMINI.md
-tech_spec/
+# Hprof files
+*.hprof