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_duplicates.py

@@ -0,0 +1,22 @@
+from __future__ import annotations
+
+from pathlib import Path
+
+from app.utils.hashing import sha256_file
+
+
+def test_two_files_with_same_content_share_sha(tmp_path: Path):
+    a = tmp_path / "a.pdf"
+    b = tmp_path / "b.pdf"
+    payload = b"%PDF-1.4\n" + b"x" * 4096
+    a.write_bytes(payload)
+    b.write_bytes(payload)
+    assert sha256_file(a) == sha256_file(b)
+
+
+def test_one_byte_difference_changes_sha(tmp_path: Path):
+    a = tmp_path / "a.pdf"
+    b = tmp_path / "b.pdf"
+    a.write_bytes(b"%PDF-1.4\n" + b"x" * 4096)
+    b.write_bytes(b"%PDF-1.4\n" + b"x" * 4095 + b"y")
+    assert sha256_file(a) != sha256_file(b)