Let imports opt out of AI classification

Classification preferences gains "Classify newly imported transactions with
AI", stored as classify_on_import in config.toml and on by default, so existing
configurations keep their behaviour. It covers CSV imports and bank
synchronization alike.

With it off, no import path contacts the provider: classification falls to the
new provider-free rules path, where an opted-in merchant rule still applies its
category and tags, an alias match still attaches its merchant, and everything
else arrives on the editable fallback without a provenance error that would
suggest the provider had failed. Analyse remains available on demand.

web/src/Settings.tsx

@@ -16,6 +16,9 @@ export function Settings({ state, mutate }: { state: State; mutate: Mutate }) {
   const [includeAmount, setIncludeAmount] = useState(
     state.settings.include_amount,
   );
+  const [classifyOnImport, setClassifyOnImport] = useState(
+    state.settings.classify_on_import,
+  );
   const [busy, setBusy] = useState(false);
   const [error, setError] = useState("");
   const [rebuild, setRebuild] = useState(false);
@@ -334,7 +337,11 @@ export function Settings({ state, mutate }: { state: State; mutate: Mutate }) {
               try {
                 await mutate(
                   "/api/settings",
-                  { model: model.trim(), include_amount: includeAmount },
+                  {
+                    model: model.trim(),
+                    include_amount: includeAmount,
+                    classify_on_import: classifyOnImport,
+                  },
                   "Classification preferences saved",
                 );
               } catch (err) {
@@ -366,6 +373,20 @@ export function Settings({ state, mutate }: { state: State; mutate: Mutate }) {
               Disabled by default for privacy. Enabling this shares the amount
               with the configured AI provider to help classification.
             </p>
+            <label className="checkbox">
+              <input
+                type="checkbox"
+                checked={classifyOnImport}
+                onChange={(e) => setClassifyOnImport(e.target.checked)}
+              />
+              Classify newly imported transactions with AI
+            </label>
+            <p className="muted small">
+              Applies to CSV imports and bank synchronization. When off, no
+              import contacts your AI provider: enabled merchant rules still
+              classify, and everything else arrives unclassified and editable.
+              AI classification → Analyse is unaffected.
+            </p>
             <button
               className="button primary"
               disabled={busy || credentialsBusy}