refactor: unify C2PA vendor registry + code-health fixes + uv publish

Three P2 cleanups from a library-wide review.

Detection -- single C2PA_AI_VENDORS registry (noai/constants.py):
- C2PA_ISSUERS, SYNTHID_C2PA_ISSUERS, and identify._ISSUER_PLATFORM now derive
  from one C2paAiVendor table, so adding a C2PA vendor is one entry instead of
  edits in three places across two files. Behavior-identical (262 detection
  tests pass; the kept `needle` field is load-bearing -- it differs from `org`
  for Google and ByteDance, with no mechanical derivation).

Code-health:
- region_eraser.erase_lama now accepts grayscale/BGRA like erase_cv2 (it
  crashed on grayscale and silently dropped alpha on BGRA). +2 regression tests.
- batch frees the device cache between images via a shared try_empty_device_cache
  helper (generalized from the MPS-only _try_clear_mps_cache, now reused by both
  the MPS->CPU fallback and the batch loop).
- batch gained --controlnet-scale (parity with invisible/all).

CI / packaging:
- publish.yml uploads via `uv publish` (PyPI trusted publishing over OIDC),
  replacing pypa/gh-action-pypi-publish so uploads no longer depend on that
  action's bundled twine accepting the Metadata-Version. Workflow filename +
  pypi environment unchanged, so PyPI's trusted-publisher entry still matches.
- hatchling pin relaxed <1.28 -> <1.31 (verified against hatch's changelog:
  1.30.0 made Metadata 2.5 the default, 1.30.1 reverted to 2.4; 1.27-1.29 were
  always 2.4). Kept as belt-and-suspenders so the first uv-publish release ships
  2.4, isolating the uploader swap from the metadata-version bump.

Docs (CLAUDE.md, pyproject) synced; corrected the inaccurate "hatchling 1.28+
emits 2.5" note.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/remove_ai_watermarks/cli.py

@@ -990,6 +990,7 @@ def _process_batch_image(
     min_resolution: int = 1024,
     restore_faces: bool = False,
     restore_faces_weight: float = 0.5,
+    controlnet_scale: float = 1.0,
 ) -> None:
     """Process a single image for batch mode.
 
@@ -1040,6 +1041,7 @@ def _process_batch_image(
                     device=None if device == "auto" else device,
                     pipeline=pipeline,
                     hf_token=hf_token,
+                    controlnet_conditioning_scale=controlnet_scale,
                 )
             engine_inv = ctx.obj["_inv_engine"]
             engine_inv.remove_watermark(
@@ -1114,6 +1116,7 @@ def _process_batch_image(
 @_restore_faces_options
 @_min_resolution_option
 @_unsharp_option
+@_controlnet_scale_option
 @click.pass_context
 def cmd_batch(
     ctx: click.Context,
@@ -1133,6 +1136,7 @@ def cmd_batch(
     min_resolution: int,
     restore_faces: bool,
     restore_faces_weight: float,
+    controlnet_scale: float,
 ) -> None:
     """Process all images in a directory."""
     _banner()
@@ -1187,6 +1191,7 @@ def cmd_batch(
                     min_resolution=min_resolution,
                     restore_faces=restore_faces,
                     restore_faces_weight=restore_faces_weight,
+                    controlnet_scale=controlnet_scale,
                 )
                 processed += 1