refactor: rename the application package to docsgpt

The backend import package is now docsgpt, the name it will carry on PyPI;
application was far too generic to install into anyone's site-packages.
git mv plus a mechanical rewrite of every import, dotted string and path
reference: 734 Python files, the compose files, Dockerfile, workflows, docs,
setup scripts, devcontainer, k8s manifests, vscode config, pytest and coverage
config, .gitignore. Behaviour is unchanged.

Kept for one release:
- A top-level application package whose meta-path finder resolves
  application.x.y to the already-imported docsgpt.x.y object, so old imports
  and entry points (celery -A application.app.celery,
  uvicorn application.asgi:asgi_app) keep working with a FutureWarning.
- Celery registers every application.* task name as an alias of its
  docsgpt.* task on start-up, so messages queued by the previous release still
  run. The redbeat key prefix moves to redbeat:docsgpt:v2: so schedule entries
  the previous release wrote are left unread instead of firing twice.

The backend image builds from the repository root (docker build -f
docsgpt/Dockerfile .) so it can ship the alias package; a root .dockerignore
allow-lists docsgpt/ and application/ and keeps caches, local data, .env
files, the sample index files and the Dockerfile out. Compose and the image
workflows point at the new context.

docsgpt/parser/file/audio_parser.py

@@ -0,0 +1,48 @@
+from pathlib import Path
+from typing import Dict, Union
+
+from docsgpt.core.settings import settings
+from docsgpt.parser.file.base_parser import BaseParser
+from docsgpt.stt.stt_creator import STTCreator
+from docsgpt.stt.upload_limits import enforce_audio_file_size_limit
+
+
+class AudioParser(BaseParser):
+    def __init__(self, parser_config=None):
+        super().__init__(parser_config=parser_config)
+        self._transcript_metadata: Dict[str, Dict] = {}
+
+    def _init_parser(self) -> Dict:
+        return {}
+
+    def parse_file(self, file: Path, errors: str = "ignore") -> Union[str, list[str]]:
+        _ = errors
+        try:
+            enforce_audio_file_size_limit(file.stat().st_size)
+        except OSError:
+            pass
+        stt = STTCreator.create_stt(settings.STT_PROVIDER)
+        result = stt.transcribe(
+            file,
+            language=settings.STT_LANGUAGE,
+            timestamps=settings.STT_ENABLE_TIMESTAMPS,
+            diarize=settings.STT_ENABLE_DIARIZATION,
+        )
+
+        transcript_metadata = {
+            "transcript_duration_s": result.get("duration_s"),
+            "transcript_language": result.get("language"),
+            "transcript_provider": result.get("provider"),
+        }
+        if result.get("segments"):
+            transcript_metadata["transcript_segments"] = result["segments"]
+
+        self._transcript_metadata[str(file)] = {
+            key: value
+            for key, value in transcript_metadata.items()
+            if value not in (None, [], {})
+        }
+        return result.get("text", "")
+
+    def get_file_metadata(self, file: Path) -> Dict:
+        return self._transcript_metadata.get(str(file), {})