Add 26 code-referenced keys to the catalog + a test that closes the gap (#1654)

LocalizationCoverageTests validated the catalog but never the code: a
String(localized:) whose key is missing from every catalog compiles
fine and silently ships its English defaultValue to all 29 non-source
locales. That blind spot let 26 keys go untranslated while CI stayed
green: the entire notices/board composer (10), the private-media
encryption warnings and delivery-failure reasons (9), both
courier-header strings, two delivery states, two media failure
reasons, and the [? people] channel row.

- All 26 keys added with full 30-locale coverage.
- New everyCodeReferencedKeyExistsInACatalog scans the source for
  literal String(localized:) keys and fails on any key absent from
  both catalogs. (The audit's original count of 17 was itself an
  undercount — its scan missed multi-line String( localized: calls;
  the test's regex does not.)

Co-authored-by: jack <jackjackbits@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

bitchatTests/LocalizationCoverageTests.swift

@@ -69,4 +69,45 @@ struct LocalizationCoverageTests {
         let missing = main.allLocales.subtracting(shareExt.allLocales).sorted()
         #expect(missing.isEmpty, "share extension is missing locales: \(missing.joined(separator: ", "))")
     }
+
+    /// The catalog tests above validate the CATALOG; this one validates the
+    /// CODE. A `String(localized:)` whose key is absent from every catalog
+    /// compiles and runs fine — it just silently ships its English
+    /// `defaultValue` to all 29 non-source locales. That blind spot let the
+    /// entire notices/board composer (10 keys), two delivery states, and two
+    /// media-failure reasons go untranslated while the coverage tests stayed
+    /// green. Interpolated keys can't be checked statically and are skipped;
+    /// every literal key must resolve.
+    @Test func everyCodeReferencedKeyExistsInACatalog() throws {
+        let main = try Self.loadCatalog("bitchat/Localizable.xcstrings")
+        let shareExt = try Self.loadCatalog("bitchatShareExtension/Localization/Localizable.xcstrings")
+        let knownKeys = Set(main.coverage.keys).union(shareExt.coverage.keys)
+
+        let pattern = try NSRegularExpression(pattern: #"String\(\s*localized:\s*"([^"\\]+)""#)
+        var missing: [String] = []
+
+        for sourceRoot in ["bitchat", "bitchatShareExtension"] {
+            let rootURL = Self.repoRoot.appendingPathComponent(sourceRoot)
+            let enumerator = try #require(FileManager.default.enumerator(
+                at: rootURL,
+                includingPropertiesForKeys: nil
+            ))
+            for case let fileURL as URL in enumerator where fileURL.pathExtension == "swift" {
+                let source = try String(contentsOf: fileURL, encoding: .utf8)
+                let range = NSRange(source.startIndex..., in: source)
+                pattern.enumerateMatches(in: source, range: range) { match, _, _ in
+                    guard let match, let keyRange = Range(match.range(at: 1), in: source) else { return }
+                    let key = String(source[keyRange])
+                    if !knownKeys.contains(key) {
+                        missing.append("\(key) (\(fileURL.lastPathComponent))")
+                    }
+                }
+            }
+        }
+
+        #expect(
+            missing.isEmpty,
+            "keys referenced in code but absent from every catalog — these ship English to all non-source locales: \(missing.sorted().joined(separator: ", "))"
+        )
+    }
 }