Add WebDAV backup, statistics, progress and dashboard

- WebDAV uploader: concurrency, request and bandwidth limits, retry with
  backoff, offline catch-up, encrypted manifests, durability tracking
- Automatic unique remote directory claimed with a conditional PUT
- AES-256-GCM client-side encryption with keyed blob names
- /stats, /progress, /progress/stream and a /dashboard page
- Own ctypes inotify binding with a compact watch tree (263 MB -> 76 MB RSS)
- Directory-path ignore patterns and a forget command
- Indexed range queries instead of LIKE for path prefixes

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_units.py

@@ -40,6 +40,14 @@ def test_filter_patterns():
     assert f.path_reason(PurePath("src/key.txt")) is None
 
 
+def test_directory_patterns():
+    f = Filters(patterns=("app/data/uploads",))
+    assert f.skip_dir("uploads", "app/data/uploads")
+    assert not f.skip_dir("uploads", "other/uploads")
+    assert f.path_reason(PurePath("app/data/uploads/a/b.txt")) == "ignored-pattern"
+    assert f.path_reason(PurePath("app/data/config.json")) is None
+
+
 def test_diff_unified():
     a = b"one\ntwo\nthree\n"
     b = b"one\n2\nthree\nfour\n"