Fix warnings and improve autocomplete positioning, add unit tests

- Remove unused variables (beforeCount, beforeFavCount)
- Remove Tx Power Level from advertising (not allowed)
- Fix autocomplete popup to appear near cursor position
- Calculate position based on nickname width and @ location
- Add comprehensive unit tests for:
  - Binary protocol encoding/decoding
  - Message padding for privacy
  - Bloom filter duplicate detection
  - BitchatMessage serialization
- Add test target to project.yml

project.yml

@@ -47,4 +47,15 @@ targets:
       CODE_SIGNING_REQUIRED: YES
       CODE_SIGNING_ALLOWED: YES
       ASSETCATALOG_COMPILER_APPICON_NAME: AppIcon
-      ASSETCATALOG_COMPILER_INCLUDE_ALL_APPICON_ASSETS: YES
+      ASSETCATALOG_COMPILER_INCLUDE_ALL_APPICON_ASSETS: YES
+  
+  bitchatTests:
+    type: bundle.unit-test
+    platform: [iOS, macOS]
+    sources:
+      - bitchatTests
+    dependencies:
+      - target: bitchat
+    settings:
+      PRODUCT_BUNDLE_IDENTIFIER: com.bitchat.tests
+      SWIFT_VERSION: 5.0