fix(feature-flags): close Phase 22 KEEP-VERIFY — 2 real defects + doc overclaims

KEEP-VERIFY re-audit of the Feature Flag configuration extension (STATUS's
"Phase 22 部署运维配置扩展"): marked ✅ but contained real code defects and
overstated completion.

Real defects fixed:
- D-22-A (High): FeatureFlagController.updateFlag used reflection
  `getMethod("set"+cap, boolean.class)` and only supported boolean flags.
  7 non-boolean flags (livenessProvider, localEvidenceAllowedTypes,
  counselingAttachmentsBucket, localEvidenceMaxFiles, localEvidenceMaxFileSizeMB,
  localEvidenceRetentionDays) failed to update via the API. Now dispatches by
  field type (boolean/int/String).
- D-22-B (Medium): `body.getOrDefault("value", false)` silently set false when
  value was missing and crashed on non-boolean casts. Now returns 400 on missing
  value / type mismatch and leaves the original value unchanged.

Doc overclaims corrected (no silent scope creep):
- T01-T05 module-toggle flags (isCounselingEnabled etc.) have zero business
  call sites -> dead config (exposed but not gating). Left for each module's
  own phase to wire; documented as residual.
- T07 private-storage bucket flags have zero references; storage already uses
  object-storage.bucket-private. Documented as residual.
- STATUS claimed "application.yml defaults (15 flags)"; yml has no `features:`
  block, defaults are Java field defaults. Functionally fine, docs corrected.

T06 upload policy verified actually enforced in LocalEligibilityService +
PhotoService (kept ✅).

Guard tests: new FeatureFlagControllerTest (7 cases: 21 keys exposed, boolean/
string/int update reflected, unknown flag / missing value / wrong type -> 400).
Negative validation: reverting to boolean-only dispatch made exactly 2 update
cases fail red, then green after restore — proves guards are real.

Full regression: 657 tests / 0 failures / 0 errors / 3 skipped (baseline 650, +7).

backend/src/main/java/com/danyang/match/platform/shared/controller/FeatureFlagController.java

@@ -34,20 +34,57 @@ public class FeatureFlagController {
     /**
      * 更新单个 Feature Flag
      * PUT /api/v1/operator/feature-flags/{flagName}
-     * Body: { "value": true }
+     * Body: { "value": <boolean|int|string> }
+     *
+     * <p>支持布尔 / 整数 / 字符串三类 flag（此前仅支持布尔，导致 7 个非布尔 flag
+     * 经 API 更新必失败）。未知 flag 或缺失 value 返回 400，且不会静默把功能置为关闭。
      */
     @PutMapping("/{flagName}")
     public ApiResponse<Map<String, Object>> updateFlag(
             @AuthenticationPrincipal OperatorPrincipal principal,
             @PathVariable String flagName,
-            @RequestBody Map<String, Boolean> body) {
-        boolean value = body.getOrDefault("value", false);
-        // 使用反射更新对应字段
+            @RequestBody Map<String, Object> body) {
+        if (!featureFlagConfig.getAllFlags().containsKey(flagName)) {
+            return ApiResponse.error(
+                com.danyang.match.platform.shared.enums.ApiResponseCode.BAD_REQUEST,
+                "未知的 Feature Flag: " + flagName);
+        }
+        if (!body.containsKey("value")) {
+            return ApiResponse.error(
+                com.danyang.match.platform.shared.enums.ApiResponseCode.BAD_REQUEST,
+                "请求体必须包含 value 字段");
+        }
+        Object value = body.get("value");
         try {
-            java.lang.reflect.Method setter = featureFlagConfig.getClass()
-                .getMethod("set" + capitalize(flagName), boolean.class);
-            setter.invoke(featureFlagConfig, value);
-            return ApiResponse.ok(Map.of("flagName", flagName, "value", value, "updated", true));
+            java.lang.reflect.Field field = featureFlagConfig.getClass().getDeclaredField(flagName);
+            Class<?> type = field.getType();
+            if (type == boolean.class || type == Boolean.class) {
+                boolean b = ((Boolean) value);
+                featureFlagConfig.getClass()
+                    .getMethod("set" + capitalize(flagName), boolean.class)
+                    .invoke(featureFlagConfig, b);
+            } else if (type == int.class || type == Integer.class) {
+                int i = ((Number) value).intValue();
+                featureFlagConfig.getClass()
+                    .getMethod("set" + capitalize(flagName), int.class)
+                    .invoke(featureFlagConfig, i);
+            } else if (type == String.class) {
+                featureFlagConfig.getClass()
+                    .getMethod("set" + capitalize(flagName), String.class)
+                    .invoke(featureFlagConfig, String.valueOf(value));
+            } else {
+                return ApiResponse.error(
+                    com.danyang.match.platform.shared.enums.ApiResponseCode.BAD_REQUEST,
+                    "不支持的 Flag 类型: " + type.getSimpleName());
+            }
+            return ApiResponse.ok(Map.of(
+                "flagName", flagName,
+                "value", featureFlagConfig.getAllFlags().get(flagName),
+                "updated", true));
+        } catch (ClassCastException e) {
+            return ApiResponse.error(
+                com.danyang.match.platform.shared.enums.ApiResponseCode.BAD_REQUEST,
+                "value 类型与 Flag " + flagName + " 不匹配: " + e.getMessage());
         } catch (Exception e) {
             return ApiResponse.error(
                 com.danyang.match.platform.shared.enums.ApiResponseCode.BAD_REQUEST,