Implement per-file import for in-progress torrents

Files within a downloading torrent are now imported as soon as their
individual progress reaches 100%, without waiting for the full torrent
to complete. A new processed_files table (info_hash, file_name) tracks
which files have been handled to avoid redundant re-hashing each poll.

- db.py: add processed_files table, is_file_processed, record_processed_file
- qbit_client.py: replace get_completed_torrents with get_torrents(filter, category)
- stash_handler.py: extract process_torrent_files helper, daemon now polls
  both downloading and completed torrents each cycle

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

db.py

@@ -23,6 +23,14 @@ def init_db(db_path):
             processed_at TEXT NOT NULL
         )
     """)
+    conn.execute("""
+        CREATE TABLE IF NOT EXISTS processed_files (
+            info_hash TEXT NOT NULL,
+            file_name TEXT NOT NULL,
+            processed_at TEXT NOT NULL,
+            PRIMARY KEY (info_hash, file_name)
+        )
+    """)
     conn.commit()
     return conn
 
@@ -50,16 +58,35 @@ def increment_seen(conn, file_hash):
 
 
 def is_torrent_processed(conn, info_hash):
-    """Check if a torrent has already been processed."""
+    """Check if a torrent has already been fully processed."""
     row = conn.execute("SELECT 1 FROM processed_torrents WHERE info_hash = ?", (info_hash,)).fetchone()
     return row is not None
 
 
 def record_torrent(conn, info_hash, torrent_name):
-    """Record a torrent as processed."""
+    """Record a torrent as fully processed."""
     now = datetime.now(timezone.utc).isoformat()
     conn.execute(
         "INSERT OR IGNORE INTO processed_torrents (info_hash, torrent_name, processed_at) VALUES (?, ?, ?)",
         (info_hash, torrent_name, now),
     )
     conn.commit()
+
+
+def is_file_processed(conn, info_hash, file_name):
+    """Check if an individual file within a torrent has already been processed."""
+    row = conn.execute(
+        "SELECT 1 FROM processed_files WHERE info_hash = ? AND file_name = ?",
+        (info_hash, file_name),
+    ).fetchone()
+    return row is not None
+
+
+def record_processed_file(conn, info_hash, file_name):
+    """Record an individual file within a torrent as processed."""
+    now = datetime.now(timezone.utc).isoformat()
+    conn.execute(
+        "INSERT OR IGNORE INTO processed_files (info_hash, file_name, processed_at) VALUES (?, ?, ?)",
+        (info_hash, file_name, now),
+    )
+    conn.commit()