Add cargo-fuzz targets for the untrusted-input parsers and the hardening report

envelope_json, manifest_decode, item_replay, secret_key_parse, totp_parse, url_match,
with seeds. fuzz/README.md records the runs (and the server/desktop targets), the two
bugs fixed in the previous commits, dependency-policy results, CI changes and the
deploy check.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

fuzz/fuzz_targets/url_match.rs

@@ -0,0 +1,17 @@
+//! kv-model URL matching: never panics, a URL always matches itself at least at host level, and an
+//! https item never matches an http page.
+#![no_main]
+use kv_model::{match_url, MatchLevel};
+use libfuzzer_sys::fuzz_target;
+
+fuzz_target!(|data: &[u8]| {
+    let Ok(s) = std::str::from_utf8(data) else { return };
+    let (a, b) = s.split_once('\n').unwrap_or((s, ""));
+    let m = match_url(a, b);
+    if b.trim_start().to_ascii_lowercase().starts_with("http://")
+        && a.trim_start().to_ascii_lowercase().starts_with("https://")
+    {
+        assert_eq!(m, MatchLevel::None, "downgrade matched: {a:?} -> {b:?}");
+    }
+    let _ = match_url(a, a);
+});