Restructure: Move final 12 root files into packages (klausur-service)

ocr/spell/  (3): smart_spell, core, text
upload/     (3): api, chunked, mobile
crawler/    (3): github, github_core, github_parsers
+ unified_grid → grid/, tesseract_extractor → ocr/engines/, htr_api → ocr/pipeline/

12 shims added. Only main.py, config.py, storage + RAG files remain at root.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

klausur-service/backend/upload_api.py

@@ -1,29 +1,4 @@
-"""
-Mobile Upload API — barrel re-export.
-
-All implementation split into:
-  upload_api_chunked — chunked upload endpoints (init, chunk, finalize, simple, status, cancel, list)
-  upload_api_mobile  — mobile HTML upload page
-
-DSGVO-konform: Data stays local in WLAN, no external transmission.
-"""
-
-from fastapi import APIRouter
-
-from upload_api_chunked import (  # noqa: F401
-    router as _chunked_router,
-    UPLOAD_DIR,
-    CHUNK_DIR,
-    EH_UPLOAD_DIR,
-    _upload_sessions,
-    InitUploadRequest,
-    InitUploadResponse,
-    ChunkUploadResponse,
-    FinalizeResponse,
-)
-from upload_api_mobile import router as _mobile_router  # noqa: F401
-
-# Composite router that includes both sub-routers
-router = APIRouter()
-router.include_router(_chunked_router)
-router.include_router(_mobile_router)
+# Backward-compat shim -- module moved to upload/api.py
+import importlib as _importlib
+import sys as _sys
+_sys.modules[__name__] = _importlib.import_module("upload.api")