fix: implement manual PNG chunk parser for reliable character card import

- Added read_png_text_chunks() function that manually parses PNG file structure
- Reads PNG chunks directly instead of relying on png crate's Info struct
- More reliable extraction of tEXt chunks with "chara" keyword
- Added debug logging (eprintln) to help diagnose import issues
- Updated read_character_card_from_png() to use manual parser as primary method
- Fixes "missing 'chara' chunk" error even when chunk exists in file
- Successfully imports both v2 and v3 character cards

test_png_reader.rs

@@ -0,0 +1,22 @@
+use png::Decoder;
+use std::io::BufReader;
+use std::fs;
+
+fn main() {
+    let file = fs::File::open("Mia Nakamura - The Working Girl.png").unwrap();
+    let decoder = Decoder::new(BufReader::new(file));
+    let reader = decoder.read_info().unwrap();
+    let info = reader.info();
+    
+    println!("Latin1 text chunks: {}", info.uncompressed_latin1_text.len());
+    for chunk in &info.uncompressed_latin1_text {
+        println!("  Keyword: '{}', Text length: {}", chunk.keyword, chunk.text.len());
+    }
+    
+    println!("UTF-8 text chunks: {}", info.utf8_text.len());
+    for chunk in &info.utf8_text {
+        println!("  Keyword: '{}'", chunk.keyword);
+    }
+    
+    println!("Compressed latin1 text chunks: {}", info.compressed_latin1_text.len());
+}