Fix swapped Sec-Fetch-* header values

[devvyt]

Problem

HeaderGenerator emits all four Sec-Fetch-* headers with values that are invalid for the header they appear on. Every generated header set is affected.

Headers from HeaderGenerator().generate(browser='chrome'), sent with requests to https://httpbin.org/headers:

Sec-Fetch-Dest: navigate
Sec-Fetch-Mode: same-site
Sec-Fetch-Site: ?1
Sec-Fetch-User: document

Header	Valid values	Currently sends
Sec-Fetch-Mode	cors, navigate, no-cors, same-origin, websocket	same-site
Sec-Fetch-Dest	document, empty, image, script, …	navigate
Sec-Fetch-Site	cross-site, same-origin, same-site, none	?1
Sec-Fetch-User	?1 (boolean, only sent when true)	document

Each value is valid, but on the wrong header.

Fix

Corrects the values in both constants to match the spec and upstream fingerprint-suite's assignment (site → same-site, mode → navigate, user → ?1, dest → document). Keys unchanged.

Sec-Fetch-Site is context-dependent in a real browser (none on a fresh top-level navigation), so this keeps upstream's same-site rather than change behavior beyond the swap.

Verification

python - <<'EOF'
import collections
from browserforge.headers import HeaderGenerator

want = {'sec-fetch-mode': 'navigate', 'sec-fetch-dest': 'document',
        'sec-fetch-site': 'same-site', 'sec-fetch-user': '?1'}
seen = collections.defaultdict(collections.Counter)
hg = HeaderGenerator()
for _ in range(200):
    h = {k.lower(): v for k, v in hg.generate(browser='chrome').items()}
    if 'sec-fetch-mode' in h:          # pre-Chrome-76 UAs correctly omit these
        for k in want:
            seen[k][h[k]] += 1

for k, v in sorted(want.items()):
    got = dict(seen[k])
    print(f"{k:16} {got}  {'OK' if set(got) == {v} else 'FAIL, expected ' + v}")
EOF

Passes on this branch, fails on main. Safari is unaffected.

[zhemaituk]

This seems related as well:

if (options['http_version'] or self.options['http_version']) == '2':
            return pascalize_headers(generated)

in generator.py.

It looks like the condition is inverted, and HTTP/2 headers are pascalized, instead of intended HTTP/1.1