Cleanup: dead code, small fixes, Library sorts, old-UI links (#620) (#621)

* refactor: remove dead and test-only code and the write-only prompt registry (#620)

Removes helpers nothing calls, test-only wrappers and their tests, the unused
config writer, three unused images, and the prompt registry the nodes wrote to
but nothing read, which grew with every run.

* fix: network-share readers, model unload off the loop, bad save requests (#620)

Every read-only SQLite open now uses one URI helper, so a library on a Windows
network share works in backups, restores, moves and history reads. Unloading a
model no longer blocks the server. A malformed /save body gets a 400, not a 500.

* feat(library): add Recently used, Most used and Name Z-A sorting (#620)

The old Dashboard's sorts the community asked for, on the Prompt library, in
saved views, and with paging through the whole list.

* feat(workspace): stop linking the old pages (#620)

They show a removal notice since 3.5.1. System no longer links them, the load
failure offers a reload and ComfyUI instead, and the README says they are going
away. The pages still work at their URLs.

database/sqlite_uri.py

@@ -0,0 +1,25 @@
+"""The read-only SQLite URI of a path, safe for Windows network shares."""
+
+import ntpath
+import os
+from pathlib import PurePosixPath, PureWindowsPath
+from urllib.parse import quote
+
+
+def readonly_uri(db_path, *, windows=None):
+    """The ``mode=ro`` SQLite URI of *db_path*, on this platform or the given one.
+
+    pathlib spells a UNC path ``\\\\server\\share\\x.db`` as
+    ``file://server/share/x.db``, a remote authority SQLite refuses to open.
+    With an empty authority (``file:////server/share/x.db``) SQLite hands
+    Windows the ``//server/share`` path, which it opens as the UNC path.
+    """
+    if windows is None:
+        windows = os.name == "nt"
+        db_path = os.path.abspath(db_path)
+    if not windows:
+        return PurePosixPath(db_path).as_uri() + "?mode=ro"
+    path = PureWindowsPath(db_path)
+    if ntpath.splitdrive(str(path))[0].startswith("\\\\"):
+        return "file:" + quote("//" + path.as_posix()) + "?mode=ro"
+    return path.as_uri() + "?mode=ro"