Fix footer version, improve PDF filter detection

- options.html/js: Footer version now reads dynamically from manifest via
  api.runtime.getManifest().version instead of hardcoded v0.3.0
- document-scanner.js: Increase FlateDecode lookback from 200 to 500 bytes
  (real PDF stream dictionaries are often larger than 200 bytes), and support
  array form /Filter [/FlateDecode] alongside the scalar form

https://claude.ai/code/session_01ReZUeR1nrYzJeX7fTqwXMw

src/lib/document-scanner.js

@@ -257,8 +257,8 @@ const DocumentScanner = {
 
         // Try to decompress if FlateDecode
         let content = streamData;
-        const filterMatch = str.slice(Math.max(0, match.index - 200), match.index)
-          .match(/\/Filter\s*\/FlateDecode/);
+        const dictSlice = str.slice(Math.max(0, match.index - 500), match.index);
+        const filterMatch = dictSlice.match(/\/Filter\s*(?:\/FlateDecode|\[\/FlateDecode\]|\[.*?\/FlateDecode.*?\])/);
 
         if (filterMatch) {
           try {