[DeckSync] Match server rows by identity and hash the whole deck

Sync keyed local files to server rows by path, but the server names a row
after the deck, not after the file, so any deck whose file name and deck name
differ uploaded again on every run. A second pass then brought the server copy
back as an extra local file.

- Match by the sidecar's row id, then guid, then content, and only then by the
  server path, so renaming either side no longer duplicates a deck.
- Key the server tree by row id: the server allows several rows with the same
  name in one folder, and keying by path silently dropped all but one.
- Stop discarding rows whose name contains '/' ("U/W Control"). They stay
  matchable, and only the download file name is sanitised.
- Build the download path from the folder plus a sanitised row name, including
  every folder segment, so a hostile server name cannot escape the deck folder.
- Download a colliding server row under a unique name and count it, instead of
  skipping it without a trace.
- Hash the whole deck instead of the card hash: SHA-1 over the native deck
  string covers name, printings, banner, tokens and sideboard plans. The client
  and the server hash the exact bytes they exchange, so both agree.

Adds deck_content_hash_test for the client/server hashing invariant and for the
name-only change the card hash cannot see.

libcockatrice_deck_list/libcockatrice/deck_list/deck_list.cpp

@@ -9,6 +9,7 @@
 #include "tree/inner_deck_list_node.h"
 
 #include <QAnyStringView>
+#include <QCryptographicHash>
 #include <QDebug>
 #include <QSet>
 #include <QSharedPointer>
@@ -453,6 +454,16 @@ void DeckList::refreshDeckHash()
     cachedDeckHash = QString();
 }
 
+QString DeckList::contentHash(const QString &nativeDeck)
+{
+    return QString::fromLatin1(QCryptographicHash::hash(nativeDeck.toUtf8(), QCryptographicHash::Sha1).toHex());
+}
+
+QString DeckList::getContentHash() const
+{
+    return contentHash(writeToString_Native());
+}
+
 /**
  * Calls a given function on each card in the deck.
  */

libcockatrice_deck_list/libcockatrice/deck_list/deck_list.h

@@ -289,6 +289,16 @@ public:
     /** @name Deck identity */
     ///@{
     QString getDeckHash() const;
+    /**
+     * @brief SHA-1 of a native deck string, covering everything the card hash
+     * ignores (name, printings, banner, tokens, comments, sideboard plans).
+     *
+     * Deck-collection sync hashes the exact string it sends or receives, so both
+     * peers compare the same bytes.
+     */
+    static QString contentHash(const QString &nativeDeck);
+    /** @brief contentHash() of this deck's native serialisation. */
+    QString getContentHash() const;
     void refreshDeckHash();
     ///@}