feat(privacy): detect an already-sanitized source

Scan now reports PrivacyScan.Sanitized {detected, markers, strong, files,
evidence}. SanitizationMarkers recognises a value slot filled with one
repeated placeholder + separators (xxxxx.xxxx.xx, x@xxxx.xxxx.xx,
000.00.00.0, a decoy timezone) - it matches the shape, not the literal "x",
so evolving the redaction mechanism still trips it.

detected requires corroboration: strong>=2, or strong>=1 && markers>=3, or
markers>=4. A single filler-looking token is reported (markers:1) but never
asserted as sanitized, so a partial future pass or a coincidence does not
read as "done". 0.0.0.0 / 000 / UTC / Etc/UTC are too plausibly intentional
and do not count.

UI: the Customer-data panel shows "файл уже обезличен" and hides the
sanitize button when detected.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014jDYM1nnoZZ3vFz23DDaV1

internal/privacy/privacy.go

@@ -48,6 +48,7 @@ func Scan(files []File) *models.PrivacyScan {
 		findings = append(findings, f)
 	}
 
+	san := newSanTally()
 	for _, file := range files {
 		if isAllowlistedFilename(file.Path) {
 			continue
@@ -56,7 +57,7 @@ func Scan(files []File) *models.PrivacyScan {
 			continue
 		}
 		scanned++
-		scanFileLines(file, emit)
+		scanFileLines(file, emit, san)
 	}
 
 	if scanned == 0 {
@@ -70,11 +71,12 @@ func Scan(files []File) *models.PrivacyScan {
 		Findings:     findings,
 		Customers:    guessCustomers(findings),
 		Summary:      summarize(findings),
+		Sanitized:    san.report(),
 	}
 	return report
 }
 
-func scanFileLines(file File, emit func(models.PrivacyFinding)) {
+func scanFileLines(file File, emit func(models.PrivacyFinding), san *sanTally) {
 	certFile := isCertFilename(file.Path)
 	sc := bufio.NewScanner(bytes.NewReader(file.Content))
 	sc.Buffer(make([]byte, 0, 64*1024), 1024*1024)
@@ -86,6 +88,9 @@ func scanFileLines(file File, emit func(models.PrivacyFinding)) {
 			line = line[:maxScanLineBytes]
 		}
 		scanLine(file.Path, line, ln, certFile, emit)
+		for _, m := range SanitizationMarkers(line) {
+			san.add(file.Path, ln, line, m)
+		}
 	}
 }