feat: Credits-System mit Verbrauchsanzeige im User-Dropdown

- DB-Migration: credits_total/credits_used/cost_per_credit auf licenses, token_usage_monthly Tabelle
- Orchestrator: Monatliche Token-Aggregation + Credits-Abzug nach Refresh
- Auth: Credits-Daten im /me Endpoint + Bugfix fehlende Klammer in get()
- Frontend: Credits-Balken im User-Dropdown mit Farbwechsel

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/database.py

@@ -582,7 +582,42 @@ async def init_db():
             await db.commit()
             logger.info("Migration: article_locations-Tabelle erstellt")
 
-        # Verwaiste running-Eintraege beim Start als error markieren (aelter als 15 Min)
+
+        # Migration: Credits-System fuer Lizenzen
+        cursor = await db.execute("PRAGMA table_info(licenses)")
+        columns = [row[1] for row in await cursor.fetchall()]
+        if "token_budget_usd" not in columns:
+            await db.execute("ALTER TABLE licenses ADD COLUMN token_budget_usd REAL")
+            await db.execute("ALTER TABLE licenses ADD COLUMN credits_total INTEGER")
+            await db.execute("ALTER TABLE licenses ADD COLUMN credits_used REAL DEFAULT 0")
+            await db.execute("ALTER TABLE licenses ADD COLUMN cost_per_credit REAL")
+            await db.execute("ALTER TABLE licenses ADD COLUMN budget_warning_percent INTEGER DEFAULT 80")
+            await db.commit()
+            logger.info("Migration: Credits-System zu Lizenzen hinzugefuegt")
+
+        # Migration: Token-Usage-Monatstabelle
+        cursor = await db.execute("SELECT name FROM sqlite_master WHERE type='table' AND name='token_usage_monthly'")
+        if not await cursor.fetchone():
+            await db.execute("""
+                CREATE TABLE token_usage_monthly (
+                    id INTEGER PRIMARY KEY AUTOINCREMENT,
+                    organization_id INTEGER REFERENCES organizations(id),
+                    year_month TEXT NOT NULL,
+                    input_tokens INTEGER DEFAULT 0,
+                    output_tokens INTEGER DEFAULT 0,
+                    cache_creation_tokens INTEGER DEFAULT 0,
+                    cache_read_tokens INTEGER DEFAULT 0,
+                    total_cost_usd REAL DEFAULT 0.0,
+                    api_calls INTEGER DEFAULT 0,
+                    refresh_count INTEGER DEFAULT 0,
+                    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+                    UNIQUE(organization_id, year_month)
+                )
+            """)
+            await db.commit()
+            logger.info("Migration: token_usage_monthly Tabelle erstellt")
+
+    # Verwaiste running-Eintraege beim Start als error markieren (aelter als 15 Min)
         await db.execute(
             """UPDATE refresh_log SET status = 'error', error_message = 'Verwaist beim Neustart',
                completed_at = CURRENT_TIMESTAMP