chore: retire iflow integration — product discontinued (#3166) (#3211)

Remove the iFlow CLI integration whose product was shut down: subpackage,
registry entry, catalog entry, docs, tests, and issue-template options.

Assisted-by: GitHub Copilot (model: Claude Opus 4.8, autonomous)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/specify_cli/integrations/__init__.py

@@ -64,7 +64,6 @@ def _register_builtins() -> None:
     from .generic import GenericIntegration
     from .goose import GooseIntegration
     from .hermes import HermesIntegration
-    from .iflow import IflowIntegration
     from .junie import JunieIntegration
     from .kilocode import KilocodeIntegration
     from .kimi import KimiIntegration
@@ -103,7 +102,6 @@ def _register_builtins() -> None:
     _register(GenericIntegration())
     _register(GooseIntegration())
     _register(HermesIntegration())
-    _register(IflowIntegration())
     _register(JunieIntegration())
     _register(KilocodeIntegration())
     _register(KimiIntegration())