added pytest test suite (174 tests)

174 tests covering URL normalization, FTS5 query sanitization, SSRF/CSRF
guards, sharing-mode logic, DB schema and upsert paths, handler
end-to-end flows, and gateway body-size / mesh-whitelist guards. Each
recent bug-fix commit (6ffd38d, 1bc695f, 8dffd8c) has an explicit
regression test in test_regressions.py. One xfail documents a minor
latent bug in clean_url where port 80 is not stripped from upgraded
https URLs.

tests/test_pagination.py

@@ -0,0 +1,58 @@
+"""Tests for `_paginate` and `_page_nav`."""
+from handlers import _paginate, _page_nav, PER_PAGE
+
+
+def test_paginate_default_is_one():
+    assert _paginate({}) == 1
+
+
+def test_paginate_reads_query_string():
+    assert _paginate({"p": ["3"]}) == 3
+
+
+def test_paginate_clamps_to_one():
+    assert _paginate({"p": ["0"]}) == 1
+    assert _paginate({"p": ["-5"]}) == 1
+
+
+def test_paginate_handles_bad_input():
+    assert _paginate({"p": ["not-a-number"]}) == 1
+    assert _paginate({"p": []}) == 1
+
+
+def test_paginate_custom_key():
+    assert _paginate({"batch": ["7"]}, key="batch") == 7
+
+
+def test_page_nav_empty_when_single_page():
+    assert _page_nav(1, PER_PAGE, "/?q=foo") == ""
+    assert _page_nav(1, 0, "/?q=foo") == ""
+
+
+def test_page_nav_shows_next_on_first_page():
+    out = _page_nav(1, PER_PAGE * 3, "/?q=foo")
+    assert "next" in out
+    assert "prev" not in out
+    assert "page 1 of 3" in out
+
+
+def test_page_nav_shows_both_in_middle():
+    out = _page_nav(2, PER_PAGE * 3, "/?q=foo")
+    assert "next" in out
+    assert "prev" in out
+
+
+def test_page_nav_shows_prev_on_last_page():
+    out = _page_nav(3, PER_PAGE * 3, "/?q=foo")
+    assert "next" not in out
+    assert "prev" in out
+    assert "page 3 of 3" in out
+
+
+def test_page_nav_handles_query_string_separator():
+    # when base_url already has ?, pagination links must use &
+    out = _page_nav(1, PER_PAGE * 2, "/?q=foo")
+    assert "&p=2" in out
+    # when base_url has no ?, pagination links use ?
+    out = _page_nav(1, PER_PAGE * 2, "/pages")
+    assert "?p=2" in out