i18n: fill all locale gaps so no string falls back to English (#1393)

Follow-up to #1391 — the Codex review flagged that the new feature-string
batch stopped at vi, omitting fil, pt-BR, zh-Hans, and zh-Hant.

- Translate the 137 feature strings into fil, pt-BR, zh-Hans, zh-Hant (548 entries)
- Translate fingerprint.message.vouched_by (plural) into the 16 locales it
  was missing, with CLDR-correct plural categories per language
- Add the 13 locales missing from the share extension catalog (78 entries),
  bringing it to the same 29 locales as the main app
- Mark the '#%@' channel-hashtag format as shouldTranslate=false like '%@'
- Add LocalizationCoverageTests: fails if any translatable key in either
  catalog is missing any supported locale, or if the share extension
  supports fewer locales than the main app

Machine translations marked needs_review, matching #1391. Verified no
existing translation was altered; full suite (1348 tests) green.

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

bitchatTests/LocalizationCoverageTests.swift

@@ -0,0 +1,74 @@
+import Testing
+import Foundation
+
+/// Guards against locale gaps in the string catalogs: every translatable key
+/// must have a localization for every supported locale, so no user ever sees
+/// an English fallback (see PR #1391 review).
+struct LocalizationCoverageTests {
+    private static let repoRoot = URL(fileURLWithPath: #filePath)
+        .deletingLastPathComponent()  // bitchatTests
+        .deletingLastPathComponent()  // repo root
+
+    private struct Catalog {
+        let sourceLanguage: String
+        /// key -> set of locales with a localization entry
+        let coverage: [String: Set<String>]
+        /// all locales appearing anywhere in the catalog
+        var allLocales: Set<String> { coverage.values.reduce(into: []) { $0.formUnion($1) } }
+    }
+
+    private static func loadCatalog(_ relativePath: String) throws -> Catalog {
+        let url = repoRoot.appendingPathComponent(relativePath)
+        let data = try Data(contentsOf: url)
+        let root = try #require(try JSONSerialization.jsonObject(with: data) as? [String: Any])
+        let strings = try #require(root["strings"] as? [String: Any])
+        let sourceLanguage = try #require(root["sourceLanguage"] as? String)
+
+        var coverage: [String: Set<String>] = [:]
+        for (key, value) in strings {
+            guard let entry = value as? [String: Any] else { continue }
+            if entry["shouldTranslate"] as? Bool == false { continue }
+            let localizations = entry["localizations"] as? [String: Any] ?? [:]
+            var locales: Set<String> = []
+            for (locale, loc) in localizations {
+                guard let loc = loc as? [String: Any] else { continue }
+                // A localization counts if it has a non-empty stringUnit value
+                // or uses variations/substitutions (plural forms).
+                if let unit = loc["stringUnit"] as? [String: Any],
+                   let unitValue = unit["value"] as? String, !unitValue.isEmpty {
+                    locales.insert(locale)
+                } else if loc["variations"] != nil || loc["substitutions"] != nil {
+                    locales.insert(locale)
+                }
+            }
+            coverage[key] = locales
+        }
+        return Catalog(sourceLanguage: sourceLanguage, coverage: coverage)
+    }
+
+    @Test func mainCatalogCoversAllLocalesForEveryKey() throws {
+        let catalog = try Self.loadCatalog("bitchat/Localizable.xcstrings")
+        let expected = catalog.allLocales
+        #expect(expected.count > 1, "catalog should declare more locales than the source language")
+        for (key, locales) in catalog.coverage.sorted(by: { $0.key < $1.key }) {
+            let missing = expected.subtracting(locales).sorted()
+            #expect(missing.isEmpty, "\(key) is missing locales: \(missing.joined(separator: ", "))")
+        }
+    }
+
+    @Test func shareExtensionCatalogCoversAllLocalesForEveryKey() throws {
+        let catalog = try Self.loadCatalog("bitchatShareExtension/Localization/Localizable.xcstrings")
+        let expected = catalog.allLocales
+        for (key, locales) in catalog.coverage.sorted(by: { $0.key < $1.key }) {
+            let missing = expected.subtracting(locales).sorted()
+            #expect(missing.isEmpty, "\(key) is missing locales: \(missing.joined(separator: ", "))")
+        }
+    }
+
+    @Test func shareExtensionSupportsSameLocalesAsMainApp() throws {
+        let main = try Self.loadCatalog("bitchat/Localizable.xcstrings")
+        let shareExt = try Self.loadCatalog("bitchatShareExtension/Localization/Localizable.xcstrings")
+        let missing = main.allLocales.subtracting(shareExt.allLocales).sorted()
+        #expect(missing.isEmpty, "share extension is missing locales: \(missing.joined(separator: ", "))")
+    }
+}