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.

tests/test_split_node.py

@@ -28,7 +28,6 @@ class TestSplitNode(unittest.TestCase):
     def test_split_encodes_composition_and_persists_main_text_with_metadata(self):
         node = PromptManagerSplit.__new__(PromptManagerSplit)
         node.logger = logging.getLogger("test.split")
-        node.comfyui_integration = unittest.mock.Mock()
         node._inject_lora_trigger_words = lambda text: text
         node._track_prompt_execution = unittest.mock.Mock(return_value=42)
         clip = unittest.mock.Mock()