Chore: Drop old signal and unneeded apps, transition to parser registry instead (#12405)

* refactor: switch consumer and callers to ParserRegistry (Phase 4)

Replace all Django signal-based parser discovery with direct registry
calls. Removes `_parser_cleanup`, `parser_is_new_style` shims, and all
old-style isinstance checks. All parser instantiation now uses the
`with parser_class() as parser:` context manager pattern.

- documents/parsers.py: delegate to get_parser_registry(); drop lru_cache
- documents/consumer.py: use registry + context manager; remove shims
- documents/tasks.py: same pattern
- documents/management/commands/document_thumbnails.py: same pattern
- documents/views.py: get_metadata uses context manager
- documents/checks.py: use get_parser_registry().all_parsers()
- paperless/parsers/registry.py: add all_parsers() public method
- tests: update mocks to target documents.consumer.get_parser_class_for_mime_type

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

* refactor: drop get_parser_class_for_mime_type; callers use registry directly

All callers now call get_parser_registry().get_parser_for_file() with
the actual filename and path, enabling score() to use file extension
hints. The MIME-only helper is removed.

- consumer.py: passes self.filename + self.working_copy
- tasks.py: passes document.original_filename + document.source_path
- document_thumbnails.py: same pattern
- views.py: passes Path(file).name + Path(file)
- parsers.py: internal helpers inline the registry call with filename=""
- test_parsers.py: drop TestParserDiscovery (was testing mock behavior);
  TestParserAvailability uses registry directly
- test_consumer.py: mocks switch to documents.consumer.get_parser_registry

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

* refactor: remove document_consumer_declaration signal infrastructure

Remove the document_consumer_declaration signal that was previously used
for parser registration. Each parser app no longer connects to this signal,
and the signal declaration itself has been removed from documents/signals.

Changes:
- Remove document_consumer_declaration from documents/signals/__init__.py
- Remove ready() methods and signal imports from all parser app configs
- Delete signal shim files (signals.py) from all parser apps:
  - paperless_tesseract/signals.py
  - paperless_text/signals.py
  - paperless_tika/signals.py
  - paperless_mail/signals.py
  - paperless_remote/signals.py

Parser discovery now happens exclusively through the ParserRegistry
system introduced in the previous refactor phases.

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

* refactor: remove empty paperless_text and paperless_tika Django apps

After parser classes were moved to paperless/parsers/ in the plugin
refactor, these Django apps contained only empty AppConfig classes
with no models, views, tasks, migrations, or other functionality.

- Remove paperless_text and paperless_tika from INSTALLED_APPS
- Delete empty app directories entirely
- Update pyproject.toml test exclusions
- Clean stale mypy baseline entries for moved parser files

paperless_remote app is retained as it contains meaningful system
checks for Azure AI configuration.

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

* Moves the checks and tests to the main application and removes the old applications

* Adds a comment to satisy Sonar

* refactor: remove automatic log_summary() call from get_parser_registry()

The summary was logged once per process, causing it to appear repeatedly
during Docker startup (management commands, web server, each Celery
worker subprocess). External parsers are already announced individually
at INFO when discovered; the full summary is redundant noise.
log_summary() is retained on ParserRegistry for manual/debug use.

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

* Cleans up the duplicate test file/fixture

* Fixes a race condition where webserver threads could race to populate the registry

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

src/documents/views.py

@@ -7,7 +7,6 @@ import tempfile
 import zipfile
 from collections import defaultdict
 from collections import deque
-from contextlib import nullcontext
 from datetime import datetime
 from pathlib import Path
 from time import mktime
@@ -159,7 +158,6 @@ from documents.models import UiSettings
 from documents.models import Workflow
 from documents.models import WorkflowAction
 from documents.models import WorkflowTrigger
-from documents.parsers import get_parser_class_for_mime_type
 from documents.permissions import AcknowledgeTasksPermissions
 from documents.permissions import PaperlessAdminPermissions
 from documents.permissions import PaperlessNotePermissions
@@ -227,7 +225,7 @@ from paperless.celery import app as celery_app
 from paperless.config import AIConfig
 from paperless.config import GeneralConfig
 from paperless.models import ApplicationConfiguration
-from paperless.parsers import ParserProtocol
+from paperless.parsers.registry import get_parser_registry
 from paperless.serialisers import GroupSerializer
 from paperless.serialisers import UserSerializer
 from paperless.views import StandardPagination
@@ -1084,17 +1082,17 @@ class DocumentViewSet(
         if not Path(file).is_file():
             return None
 
-        parser_class = get_parser_class_for_mime_type(mime_type)
+        parser_class = get_parser_registry().get_parser_for_file(
+            mime_type,
+            Path(file).name,
+            Path(file),
+        )
         if parser_class:
-            parser = parser_class(progress_callback=None, logging_group=None)
-            cm = parser if isinstance(parser, ParserProtocol) else nullcontext(parser)
-
             try:
-                with cm:
+                with parser_class() as parser:
                     return parser.extract_metadata(file, mime_type)
             except Exception:  # pragma: no cover
                 logger.exception(f"Issue getting metadata for {file}")
-                # TODO: cover GPG errors, remove later.
                 return []
         else:  # pragma: no cover
             logger.warning(f"No parser for {mime_type}")