v1.0.3: Fix TipTap JSON content conversion for editor display

- Replace all TypeToken usage with JsonParser/gson.fromJson (fixes R8/ProGuard crash)
- Add parseJsonArray/parseJsonObject helpers for API response parsing
- Fix contentToMarkdown to properly convert TipTap JSON objects to Markdown
  using tiptapToMarkdown instead of returning raw JSON
- Fix API endpoints to handle unwrapped response formats
- Add ProGuard rules for Gson TypeToken preservation
- Redirect build dir to /tmp for Samba compatibility

app/proguard-rules.pro

@@ -2,5 +2,14 @@
 -keepattributes Signature
 -keepattributes *Annotation*
 -keep class com.docmost.app.api.** { *; }
+-keep class com.docmost.app.data.** { *; }
 -dontwarn okhttp3.**
 -dontwarn okio.**
+
+# Gson - preserve TypeToken anonymous subclasses and generic signatures
+-keep class com.google.gson.** { *; }
+-keep class * extends com.google.gson.reflect.TypeToken { *; }
+-keep class * extends com.google.gson.TypeAdapter { *; }
+-keepattributes Signature
+-keepattributes RuntimeVisibleAnnotations
+-keep class sun.misc.Unsafe { *; }