Add cover page support with Chinese font rendering

Features:
- Cover page generation using Python/Pillow with Apple PingFang font
- CLI commands: cover-create, job-cover for cover page management
- API endpoints: PUT /api/fax/jobs/{id}/cover for cover modification
- Send fax with cover page: --to, --from, --subject, --note options
- Multi-page TIFF parsing for PDF conversion (fix: all pages now sent)
- Preview HTML generation with pan/zoom support
- OCR verification for cover page content
- Class 2 receive support for incoming faxes

Fixes:
- Modem initialization before Class 2 mode entry
- Dial timeout handling with retry logic
- Multi-page fax transmission between pages
- Chinese character rendering in cover pages (Apple native fonts)

src/queue/job.rs

@@ -24,6 +24,10 @@ pub struct FaxJob {
     pub retries: u8,
     pub created_at: DateTime<Utc>,
     pub updated_at: DateTime<Utc>,
+    pub cover_to: Option<String>,
+    pub cover_from: Option<String>,
+    pub cover_subject: Option<String>,
+    pub cover_notes: Option<String>,
 }
 
 impl FaxJob {
@@ -38,6 +42,10 @@ impl FaxJob {
             retries: 0,
             created_at: now,
             updated_at: now,
+            cover_to: None,
+            cover_from: None,
+            cover_subject: None,
+            cover_notes: None,
         }
     }
 }