feat(core): ManaAppLog + appGroup/logSubsystem in ManaAppConfig (v1.7.0)

Audit 2026-05-17 V4. Ersetzt das hand-getippte Log.swift-Boilerplate
in jeder App durch einen Config-getriebenen Wrapper.

Neu:
- `ManaAppLog` — Factory fuer OSLog-Logger gegen ein ManaAppConfig.
  Standard-Kategorien app/auth/api/db/web, plus `category("…")` fuer
  app-spezifische Kategorien.
- `ManaAppConfig.appGroup: String?` (default nil) — Single-Source fuer
  den App-Group-String, der heute in jeder App 3-4× hardcoded steht.
- `ManaAppConfig.logSubsystem: String` (default = keychainService) —
  Subsystem fuer ManaAppLog.

Nichts breaking — beide neuen Felder haben Default-Implementations,
DefaultManaAppConfig.init hat zwei zusaetzliche optionale Parameter.

Tests: 4 neue ManaAppConfig-Tests + 5 neue ManaAppLog-Tests.
85/85 gruen (vorher 76/76).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Tests/ManaCoreTests/ManaAppConfigTests.swift

@@ -24,4 +24,42 @@ struct ManaAppConfigTests {
         )
         #expect(config.keychainAccessGroup == nil)
     }
+
+    @Test("AppGroup ist optional, default nil")
+    func appGroupDefaultsNil() {
+        let config = DefaultManaAppConfig(
+            authBaseURL: URL(string: "https://auth.mana.how")!,
+            keychainService: "ev.mana.cards"
+        )
+        #expect(config.appGroup == nil)
+    }
+
+    @Test("AppGroup wird durchgereicht wenn gesetzt")
+    func appGroupPassedThrough() {
+        let config = DefaultManaAppConfig(
+            authBaseURL: URL(string: "https://auth.mana.how")!,
+            keychainService: "ev.mana.cards",
+            appGroup: "group.ev.mana.cards"
+        )
+        #expect(config.appGroup == "group.ev.mana.cards")
+    }
+
+    @Test("LogSubsystem default = keychainService")
+    func logSubsystemDefaultsToKeychainService() {
+        let config = DefaultManaAppConfig(
+            authBaseURL: URL(string: "https://auth.mana.how")!,
+            keychainService: "ev.mana.cards"
+        )
+        #expect(config.logSubsystem == "ev.mana.cards")
+    }
+
+    @Test("LogSubsystem kann explizit überschrieben werden")
+    func logSubsystemOverride() {
+        let config = DefaultManaAppConfig(
+            authBaseURL: URL(string: "https://auth.mana.how")!,
+            keychainService: "ev.mana.cards",
+            logSubsystem: "ev.mana.cards.debug"
+        )
+        #expect(config.logSubsystem == "ev.mana.cards.debug")
+    }
 }

Tests/ManaCoreTests/ManaAppLogTests.swift

@@ -0,0 +1,53 @@
+import Foundation
+import Testing
+@testable import ManaCore
+
+@Suite("ManaAppLog")
+struct ManaAppLogTests {
+    @Test("Init aus Config nimmt logSubsystem")
+    func initFromConfig() {
+        let config = DefaultManaAppConfig(
+            authBaseURL: URL(string: "https://auth.mana.how")!,
+            keychainService: "ev.mana.cards"
+        )
+        let log = ManaAppLog(config)
+        #expect(log.subsystem == "ev.mana.cards")
+    }
+
+    @Test("Explizit gesetztes logSubsystem überschreibt keychainService")
+    func initFromConfigWithCustomSubsystem() {
+        let config = DefaultManaAppConfig(
+            authBaseURL: URL(string: "https://auth.mana.how")!,
+            keychainService: "ev.mana.cards",
+            logSubsystem: "ev.mana.cards.test"
+        )
+        let log = ManaAppLog(config)
+        #expect(log.subsystem == "ev.mana.cards.test")
+    }
+
+    @Test("Direkter String-Constructor")
+    func initFromString() {
+        let log = ManaAppLog(subsystem: "ev.mana.test")
+        #expect(log.subsystem == "ev.mana.test")
+    }
+
+    @Test("Standard-Kategorien sind erreichbar")
+    func standardCategoriesExist() {
+        let log = ManaAppLog(subsystem: "ev.mana.test")
+        // Logger ist nicht Equatable, aber wir können Existenz prüfen
+        // indem wir den Wert binden — Compile genügt.
+        let _ = log.app
+        let _ = log.auth
+        let _ = log.api
+        let _ = log.db
+        let _ = log.web
+    }
+
+    @Test("category() liefert beliebige Custom-Kategorie")
+    func customCategory() {
+        let log = ManaAppLog(subsystem: "ev.mana.test")
+        let _ = log.category("study")
+        let _ = log.category("tracking")
+        let _ = log.category("llm")
+    }
+}