Clean up leftover quoted-printable artifacts in email body

Add a second-pass QP decode to catch =XX sequences that survive
the initial mailparse decoding.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Cargo.lock

@@ -1549,7 +1549,9 @@ dependencies = [
  "imap",
  "mailparse",
  "native-tls",
+ "quoted_printable",
  "ratatui",
+ "regex",
  "serde",
  "toml",
 ]

Cargo.toml

@@ -13,3 +13,5 @@ toml = "1.0"
 chrono = "0.4"
 mailparse = "0.15"
 html2text = "0.14"
+quoted_printable = "0.5"
+regex = "1"

src/inbox.rs

@@ -180,14 +180,25 @@ fn extract_plain_text(raw: &[u8]) -> Result<String, String> {
     let parsed = mailparse::parse_mail(raw).map_err(|e| e.to_string())?;
     // Try text/plain first
     if let Some(text) = find_part(&parsed, "text/plain") {
-        return Ok(text);
+        return Ok(clean_text(&text));
     }
     // Fall back to text/html rendered as text
     if let Some(html) = find_part(&parsed, "text/html") {
-        return Ok(html_to_text(&html));
+        return Ok(clean_text(&html_to_text(&html)));
     }
     // Last resort: top-level body
-    parsed.get_body().map_err(|e| e.to_string())
+    parsed.get_body().map(|s| clean_text(&s)).map_err(|e| e.to_string())
+}
+
+/// Remove leftover quoted-printable artifacts (=XX sequences)
+fn clean_text(text: &str) -> String {
+    let re = regex::Regex::new(r"=[0-9A-Fa-f]{2}").unwrap();
+    // Try to decode any remaining QP sequences
+    let decoded = quoted_printable::decode(text.as_bytes(), quoted_printable::ParseMode::Robust);
+    match decoded {
+        Ok(bytes) => String::from_utf8_lossy(&bytes).to_string(),
+        Err(_) => re.replace_all(text, "").to_string(),
+    }
 }
 
 fn find_part(mail: &mailparse::ParsedMail, mime_type: &str) -> Option<String> {