fix(inbounds): reject incompatible VLESS fallbacks and prevent Xray crashes (#7003)

Xray refuses a VLESS inbound with server decryption whenever fallbacks is non-nil, even an empty list, so an API or imported inbound with decryption and fallbacks: [] took every inbound down. Empty fallback arrays are now normalized away on add, update, config build and node push; non-empty ones are refused with decryption, enabling decryption over stored fallback rules is refused, and a legacy conflicting row holds back the running core instead of stopping it. The form, API docs and locales follow. Closes #7001.

.github/workflows/ci.yml

@@ -75,12 +75,12 @@ jobs:
       - name: PostgreSQL durable-first tests
         run: |
           set -o pipefail
-          go test ./internal/web/service -run 'PostgresCommitFailure|^TestSyncInboundClientsOnPostgres$|^TestSetClientLimitHwidIsSerializedWithSyncInbound$' -count=1 -v | tee /tmp/postgres-durable-first.log
+          go test ./internal/web/service -run 'PostgresCommitFailure|^TestSyncInboundClientsOnPostgres$|^TestSetClientLimitHwidIsSerializedWithSyncInbound$|^TestVlessManagedFallbackConflictPostgres$' -count=1 -v | tee /tmp/postgres-durable-first.log
           # Count passes rather than assert no SKIP: a renamed or deleted test
           # prints "no tests to run" and exits 0, leaving the step green for nothing.
           passed=$(grep -c -- '^--- PASS' /tmp/postgres-durable-first.log || true)
-          if [ "$passed" -lt 4 ]; then
-            echo "expected at least 4 passing durable-first tests, got $passed" >&2
+          if [ "$passed" -lt 5 ]; then
+            echo "expected at least 5 passing durable-first tests, got $passed" >&2
             exit 1
           fi