feat: migrate receiptwitness to standalone repo with inlined common

Extract receiptwitness/ from the monorepo into cartsnitch/receiptwitness.
Inline the consumed modules from cartsnitch-common so there is no
cross-repo dependency.

- Add src/receiptwitness/shared/ with inlined models, schemas, constants, database
- Update all imports from cartsnitch_common to receiptwitness.shared
- Remove cartsnitch-common dependency from pyproject.toml
- Copy and update Alembic config (alembic.ini, alembic/)
- Update Dockerfile for standalone build context, add migration CMD
- Add CI workflow with lint, test, build, grype scan, deploy-dev, deploy-uat
- Add .grype.yaml

Co-Authored-By: Paperclip <noreply@paperclip.ing>

pyproject.toml

@@ -8,7 +8,8 @@ version = "0.1.0"
 description = "CartSnitch receipt/purchase history ingestion service"
 requires-python = ">=3.12"
 dependencies = [
-    "cartsnitch-common>=0.1.0",
+    "alembic>=1.13,<2.0",
+    "pydantic[email]>=2.0,<3.0",
     "playwright>=1.49,<2.0",
     "playwright-stealth>=1.0,<2.0",
     "cryptography>=46.0,<47.0",
@@ -50,10 +51,6 @@ strict = false
 warn_return_any = true
 warn_unused_ignores = true
 
-[[tool.mypy.overrides]]
-module = "cartsnitch_common.*"
-ignore_missing_imports = true
-
 [tool.pytest.ini_options]
 asyncio_mode = "auto"
 testpaths = ["tests"]