feat: Phase 2 – Budget-Engine + Direktzugriff (http://IP:Port)

Budget:
- Modelle + Migration 0003: budget_template_lines, planned_income_lines,
  budget_periods, budget_period_lines.
- services/budget: Perioden-Grenzen (einstellbarer Starttag, Label nach Endmonat),
  Standard-Vorlage vs. Monats-Override (Snapshot-on-Customize), Soll/Ist inkl.
  budgetierter Sparen-Transfers, geplante Einnahmen (Soll/Ist).
- routers/budgets: Vorlage, geplante Einnahmen (CRUD), Monats-Soll/Ist,
  Monats-Override, Zurücksetzen. pytest: Perioden, Soll/Ist, Override/Reset, Einnahmen.
- Frontend: Budget-Seite (Monat + Standard-Budget), Fortschrittsbalken grün/rot,
  Monats-Navigation, editierbare Soll-Beträge; Sparen-Option im Transfer-Formular.

Deployment-Fix (Nutzer-Anforderung: http://IP:Port muss funktionieren):
- Dienst bindet an APP_BIND_HOST=0.0.0.0 (direkt im LAN erreichbar).
- APP_COOKIE_SECURE=false als Standard (sonst kein Login über reines HTTP);
  für reinen HTTPS-Betrieb umstellbar. Doku + install.sh entsprechend angepasst.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/tests/test_budget.py

@@ -0,0 +1,104 @@
+from datetime import date
+
+
+def test_period_bounds_and_labels():
+    from app.services import budget
+
+    # Gehalt am 25.: September-Budget läuft 25.08.–24.09.
+    assert budget.period_bounds("2026-09", 25) == (date(2026, 8, 25), date(2026, 9, 24))
+    # Starttag 1: Kalendermonat.
+    assert budget.period_bounds("2026-09", 1) == (date(2026, 9, 1), date(2026, 9, 30))
+    # Label-Zuordnung
+    assert budget.period_of(date(2026, 8, 27), 25) == "2026-09"
+    assert budget.period_of(date(2026, 9, 10), 25) == "2026-09"
+    assert budget.period_of(date(2026, 9, 26), 25) == "2026-10"
+    assert budget.period_of(date(2026, 9, 15), 1) == "2026-09"
+    assert budget.shift_label("2026-09", 1) == "2026-10"
+    assert budget.shift_label("2026-01", -1) == "2025-12"
+
+
+def _lebensmittel(admin):
+    groups = admin.get("/api/categories").json()
+    for g in groups:
+        for c in g["categories"]:
+            if c["name"] == "Lebensmittel":
+                return c["id"]
+    raise AssertionError("Lebensmittel-Kategorie fehlt")
+
+
+def _gehalt(admin):
+    groups = admin.get("/api/categories").json()
+    for g in groups:
+        for c in g["categories"]:
+            if c["name"] == "Gehalt":
+                return c["id"]
+    raise AssertionError("Gehalt-Kategorie fehlt")
+
+
+def test_budget_soll_ist_and_override(admin):
+    # Starttag 1 -> aktueller Zeitraum = Kalendermonat, heutige Buchungen zählen.
+    admin.put("/api/settings/budget_start_day", params={"value": "1"})
+    today = date.today()
+    label = f"{today.year:04d}-{today.month:02d}"
+
+    acc = admin.post("/api/accounts", json={"name": "Budgetkonto", "currency": "EUR"}).json()
+    leb = _lebensmittel(admin)
+
+    # Standard-Budget für Lebensmittel: 500,00 EUR.
+    admin.put(f"/api/budget/template/category/{leb}", params={"planned_cents": 50000})
+
+    # Ausgabe 300,00 EUR heute.
+    admin.post("/api/transactions", json={"type": "expense", "date": str(today), "account_id": acc["id"], "amount_cents": 30000, "category_id": leb})
+
+    v = admin.get("/api/budget/current").json()
+    row = next(c for g in v["groups"] for c in g["categories"] if c["category_id"] == leb)
+    assert row["planned_cents"] == 50000
+    assert row["actual_cents"] == 30000
+    assert row["over"] is False
+    assert v["customized"] is False
+
+    # Noch 300 EUR -> insgesamt 600 > 500 -> über Budget.
+    admin.post("/api/transactions", json={"type": "expense", "date": str(today), "account_id": acc["id"], "amount_cents": 30000, "category_id": leb})
+    v = admin.get(f"/api/budget/{label}").json()
+    row = next(c for g in v["groups"] for c in g["categories"] if c["category_id"] == leb)
+    assert row["actual_cents"] == 60000
+    assert row["over"] is True
+
+    # Monats-Override auf 700 EUR -> nicht mehr über Budget, Monat individualisiert.
+    v = admin.put(f"/api/budget/{label}/category/{leb}", params={"planned_cents": 70000}).json()
+    row = next(c for g in v["groups"] for c in g["categories"] if c["category_id"] == leb)
+    assert row["planned_cents"] == 70000
+    assert row["over"] is False
+    assert v["customized"] is True
+
+    # Vorlage bleibt unverändert.
+    tpl = admin.get("/api/budget/template").json()
+    tpl_leb = next(l for l in tpl["lines"] if l["category_id"] == leb)
+    assert tpl_leb["planned_cents"] == 50000
+
+    # Zurücksetzen -> wieder Vorlagenwert, nicht mehr individualisiert.
+    v = admin.delete(f"/api/budget/{label}").json()
+    row = next(c for g in v["groups"] for c in g["categories"] if c["category_id"] == leb)
+    assert row["planned_cents"] == 50000
+    assert v["customized"] is False
+
+
+def test_planned_income(admin):
+    admin.put("/api/settings/budget_start_day", params={"value": "1"})
+    today = date.today()
+    acc = admin.post("/api/accounts", json={"name": "Lohnkonto", "currency": "EUR"}).json()
+    gehalt = _gehalt(admin)
+
+    r = admin.post("/api/budget/income", json={
+        "label": "Gehalt", "category_id": gehalt, "target_account_id": acc["id"], "planned_cents": 300000,
+    })
+    assert r.status_code == 201
+
+    # Tatsächliche Einnahme 3000 EUR.
+    admin.post("/api/transactions", json={"type": "income", "date": str(today), "account_id": acc["id"], "amount_cents": 300000, "category_id": gehalt})
+
+    v = admin.get("/api/budget/current").json()
+    line = next(i for i in v["income"] if i["label"] == "Gehalt")
+    assert line["planned_cents"] == 300000
+    assert line["received_cents"] == 300000
+    assert v["totals"]["planned_income"] >= 300000