Merge bitcoin#28741: refactor: Fix bugprone-string-constructor warning

fa56067 refactor: Fix bugprone-string-constructor warning (MarcoFalke)

Pull request description:

  String literals in C++ have a trailing null character, so the current code is fine to rely on that implicitly. However,
  * the sqlite documentation explicitly mentions the null character
  * code readers may wonder if the code is intentional
  * clang-tidy warns about the code via `bugprone-string-constructor`

  Address the points by putting the null character into the code and enable the clang-tidy `bugprone-string-constructor` check.

ACKs for top commit:
  stickies-v:
    ACK fa56067

Tree-SHA512: da519184d792a885a8151ffc44c8da5781f5aaae12ef768a187cc6d9e542ca8952aebc2ec6c1a05f673f29a86ef44902ee96e7b491af7b4705ad38e14624882e

Author: fanquake

src/.clang-tidy

@@ -2,6 +2,7 @@ Checks: '
 -*,
 bitcoin-*,
 bugprone-argument-comment,
+bugprone-string-constructor,
 bugprone-use-after-move,
 bugprone-lambda-function-name,
 misc-unused-using-decls,

src/wallet/db.cpp

@@ -129,9 +129,9 @@ bool IsSQLiteFile(const fs::path& path)
 
     file.close();
 
-    // Check the magic, see https://sqlite.org/fileformat2.html
+    // Check the magic, see https://sqlite.org/fileformat.html
     std::string magic_str(magic, 16);
-    if (magic_str != std::string("SQLite format 3", 16)) {
+    if (magic_str != std::string{"SQLite format 3\000", 16}) {
         return false;
     }