fix: security audit — patch vulnerabilities V-02 through V-16

- V-02: XSS via innerHTML in profile.js — wrap err.message in escapeHtml()
- V-03: IDOR upload to other users' folders — add folder ownership check
- V-04: IDOR create folders in other users' trees — add parent ownership check
- V-06: Content-Disposition header injection — RFC 5987 percent-encoding
- V-08: WebDAV MOVE/COPY destination without ownership — add assert_owner checks
- V-09: .gitignore missing cert/key patterns — add *.pem, *.key, *.p12, etc.
- V-11: Username accepts XSS payloads — restrict to [a-zA-Z0-9._-]
- V-12: Minimal email validation — reject forbidden chars, require domain dot
- V-13: admin_reset_password doesn't invalidate sessions — revoke all sessions
- V-14: Rate limiting bypassable via X-Forwarded-For — gate behind OXICLOUD_TRUST_PROXY_HEADERS
- V-15: Cookie Secure flag off by default — default to true (safe-by-default)
- V-16: LIKE wildcard injection in searches — add like_escape() helper across 9 sites

src/infrastructure/repositories/pg/mod.rs

@@ -38,3 +38,16 @@ pub use settings_pg_repository::SettingsPgRepository;
 pub use share_pg_repository::SharePgRepository;
 pub use trash_db_repository::TrashDbRepository;
 pub use user_pg_repository::UserPgRepository;
+
+// ── SQL helpers ─────────────────────────────────────────────────────────────
+
+/// Escape SQL `LIKE` / `ILIKE` wildcard characters (`%` and `_`) in user
+/// input and wrap the result in `%…%` for a contains-match.
+///
+/// Without this, a user searching for `100%` would match *every* row because
+/// `%` is a wildcard in LIKE patterns.
+#[inline]
+pub fn like_escape(raw: &str) -> String {
+    let escaped = raw.replace('\\', "\\\\").replace('%', "\\%").replace('_', "\\_");
+    format!("%{escaped}%")
+}