feat(workers): Python skeleton + config + structlog

Plan 4 Phase A scaffolding. void-workers package at /workers/, sibling
of /lib/. pyproject.toml pins Python 3.12 with separate extras for
pdf / image / video / test.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

workers/void_workers/log.py

@@ -0,0 +1,16 @@
+import logging
+import structlog
+
+def init():
+    structlog.configure(
+        processors=[
+            structlog.contextvars.merge_contextvars,
+            structlog.processors.add_log_level,
+            structlog.processors.TimeStamper(fmt="iso"),
+            structlog.processors.JSONRenderer(),
+        ],
+        wrapper_class=structlog.make_filtering_bound_logger(logging.INFO),
+    )
+    return structlog.get_logger()
+
+log = init()