feature: шум canvas с seed профиля — отпечатки профилей различаются (#89)

Минимальный init-script (src/api/js/canvas_noise.js): младший бит у ~1/64 непрозрачных
пикселей при toDataURL/toBlob/getImageData, детерминирован от seed профиля. Пустой
canvas не меняется, подменённые функции неотличимы по toString и length. Старые
профили получают seed, экран сохраняется.

Проверено: 4 профиля — 4 разных хеша canvas; Cloudflare 6/6 на новых профилях.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/unit/test_profile.py

@@ -11,6 +11,7 @@ def test_fingerprint_generated_once(tmp_path):
 	screen = first["fingerprint"]["screen"]
 	assert screen["width"] >= profile.MIN_SCREEN[0] and screen["height"] >= profile.MIN_SCREEN[1]
 	assert first["fingerprint"]["device_scale_factor"] >= 1
+	assert first["fingerprint"]["canvas_seed"] > 0
 	assert "user_agent" not in first
 
 
@@ -38,9 +39,33 @@ def test_generate_falls_back_when_browserforge_fails(monkeypatch):
 			raise ValueError("Cannot generate headers")
 
 	monkeypatch.setattr(profile, "FingerprintGenerator", Failing)
-	assert profile.generate_fingerprint(attempts=2) == {"screen": {"width": 1920, "height": 1080}, "device_scale_factor": 1}
+	fp = profile.generate_fingerprint(attempts=2)
+	assert (fp["screen"], fp["device_scale_factor"]) == ({"width": 1920, "height": 1080}, 1)
+	assert fp["canvas_seed"] > 0
 
 
-def test_browser_kwargs_do_not_touch_user_agent():
-	kwargs = profile.browser_kwargs({"fingerprint": {"screen": {"width": 2560, "height": 1440}, "device_scale_factor": 1.25}})
-	assert kwargs == {"additional_args": {"screen": {"width": 2560, "height": 1440}, "device_scale_factor": 1.25}}
+def test_browser_kwargs():
+	kwargs = profile.browser_kwargs({"fingerprint": {
+		"screen": {"width": 2560, "height": 1440}, "device_scale_factor": 1.25, "canvas_seed": 12345,
+	}})
+	assert kwargs["additional_args"] == {"screen": {"width": 2560, "height": 1440}, "device_scale_factor": 1.25}
+	assert "useragent" not in kwargs
+	script = kwargs["init_script_content"]
+	assert "const SEED = 12345 | 0;" in script and "__SEED__" not in script
+
+
+def test_profile_before_canvas_noise_gets_seed_and_keeps_screen(tmp_path):
+	old = {"fingerprint": {"screen": {"width": 2560, "height": 1440}, "device_scale_factor": 2}}
+	(tmp_path / profile.SETTINGS_FILE).write_text(json.dumps(old))
+	fp = profile.load_or_create(tmp_path)["fingerprint"]
+	assert (fp["screen"], fp["device_scale_factor"]) == ({"width": 2560, "height": 1440}, 2)
+	assert fp["canvas_seed"] > 0
+	assert profile.load_or_create(tmp_path)["fingerprint"] == fp
+
+
+def test_profiles_get_different_canvas_seeds(tmp_path):
+	seeds = set()
+	for i in range(20):
+		(tmp_path / str(i)).mkdir()
+		seeds.add(profile.load_or_create(tmp_path / str(i))["fingerprint"]["canvas_seed"])
+	assert len(seeds) == 20