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>

web/src/pages/Transactions.jsx

@@ -12,6 +12,8 @@ import { centsToInput, parseAmountToCents, todayIso } from "../format";
 
 const TYPES = ["expense", "income", "transfer"];
 
+const SAVINGS_TYPES = ["sparkonto", "depot"];
+
 function emptyForm() {
   return {
     type: "expense",
@@ -23,6 +25,8 @@ function emptyForm() {
     to_amount: "",
     payee: "",
     description: "",
+    budget_as_expense: true,
+    budget_category_id: "",
   };
 }
 
@@ -69,6 +73,22 @@ export default function Transactions() {
   const fromAcc = form && accountById[Number(form.account_id)];
   const toAcc = form && accountById[Number(form.to_account_id)];
   const crossCurrency = form?.type === "transfer" && fromAcc && toAcc && fromAcc.currency !== toAcc.currency;
+  const savingsDest = form?.type === "transfer" && toAcc && SAVINGS_TYPES.includes(toAcc.type);
+
+  // Standard-Kategorie für budgetierte Sparen-Transfers (falls vorhanden).
+  const expenseGroups = useMemo(() => groups.filter((g) => g.kind === "expense"), [groups]);
+  const sparenCatId = useMemo(() => {
+    for (const g of expenseGroups)
+      for (const c of g.categories) if (c.name === "Sparen & Investments") return String(c.id);
+    return expenseGroups[0]?.categories?.[0] ? String(expenseGroups[0].categories[0].id) : "";
+  }, [expenseGroups]);
+
+  // Bei Spar-/Depot-Ziel eine Budget-Kategorie vorbelegen.
+  useEffect(() => {
+    if (savingsDest && form && !form.budget_category_id) {
+      setForm((f) => (f && !f.budget_category_id ? { ...f, budget_category_id: sparenCatId } : f));
+    }
+  }, [savingsDest, sparenCatId]);
 
   // Bei währungsübergreifenden Transfers den Zielbetrag per EZB-Kurs vorschlagen.
   useEffect(() => {
@@ -102,6 +122,8 @@ export default function Transactions() {
       to_amount: tx.to_amount_cents ? centsToInput(tx.to_amount_cents) : "",
       payee: tx.payee || "",
       description: tx.description || "",
+      budget_as_expense: tx.budget_treatment !== "neutral",
+      budget_category_id: tx.budget_category_id ? String(tx.budget_category_id) : "",
     });
   }
 
@@ -129,6 +151,11 @@ export default function Transactions() {
       body.to_account_id = Number(form.to_account_id);
       const toCents = parseAmountToCents(form.to_amount);
       if (toCents) body.to_amount_cents = toCents;
+      if (savingsDest) {
+        body.budget_treatment = form.budget_as_expense ? "budgeted" : "neutral";
+        body.budget_category_id =
+          form.budget_as_expense && form.budget_category_id ? Number(form.budget_category_id) : null;
+      }
     } else {
       body.category_id = form.category_id ? Number(form.category_id) : null;
     }
@@ -320,6 +347,28 @@ export default function Transactions() {
               )}
             </div>
 
+            {savingsDest && (
+              <div className="savings-opt">
+                <label className="checkline">
+                  <input type="checkbox" checked={form.budget_as_expense}
+                         onChange={(e) => setForm({ ...form, budget_as_expense: e.target.checked })} />
+                  <span>{t("transactions.budgetAsSavings")}</span>
+                </label>
+                {form.budget_as_expense && (
+                  <label>
+                    <span>{t("transactions.budgetCategory")}</span>
+                    <select value={form.budget_category_id} onChange={(e) => setForm({ ...form, budget_category_id: e.target.value })}>
+                      {expenseGroups.map((g) => (
+                        <optgroup key={g.id} label={g.name}>
+                          {g.categories.map((c) => <option key={c.id} value={c.id}>{c.name}</option>)}
+                        </optgroup>
+                      ))}
+                    </select>
+                  </label>
+                )}
+              </div>
+            )}
+
             {form.type !== "transfer" && (
               <div className="row">
                 <label className="grow">