chore: bootstrap repository with governance docs

Initialize git, add Apache-2.0 LICENSE, .gitattributes (LF line
endings), AGENTS.md (entry points, stack, discovery order, baseline
checks), RUNBOOK.md (dev boot, prod deploy with overlay, ingestion,
failures, rollback, scaling notes), .env.prod.example with rotated
credential placeholders, and dev-only warnings on .env.example.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/test_hashing.py

@@ -0,0 +1,26 @@
+from __future__ import annotations
+
+import hashlib
+from pathlib import Path
+
+from app.utils.hashing import sha256_bytes, sha256_file
+
+
+def test_sha256_bytes_matches_hashlib():
+    data = b"legacyhub" * 1000
+    assert sha256_bytes(data) == hashlib.sha256(data).hexdigest()
+
+
+def test_sha256_file_streaming_matches_hashlib(tmp_path: Path):
+    payload = b"\x01\x02\x03" * 5_000_000  # 15 MiB - exercises chunking
+    target = tmp_path / "blob.bin"
+    target.write_bytes(payload)
+    assert sha256_file(target) == hashlib.sha256(payload).hexdigest()
+
+
+def test_sha256_file_distinguishes_content(tmp_path: Path):
+    a = tmp_path / "a.bin"
+    b = tmp_path / "b.bin"
+    a.write_bytes(b"alpha")
+    b.write_bytes(b"beta")
+    assert sha256_file(a) != sha256_file(b)