docs: add Aquarius LP incentivization integration guide (#115)

- New guides/integrations/aquarius.mdx covering the full
  provide-liquidity → stealth-claim → withdrawal flow
- LP deposit and reward accrual via @aquariusdefi/sdk
- Stealth address generation and reward claiming with Wraith
- Testnet constants and mainnet reference table
- Privacy checklist, error table, managed agent shortcut
- Add 'Integrations' nav group to docs.json

Author: obafemimathew01-hue

docs.json

@@ -127,6 +127,12 @@
               "guides/spectre-stellar-cookbook"
             ]
           },
+          {
+            "group": "Integrations",
+            "pages": [
+              "guides/integrations/aquarius"
+            ]
+          },
           {
             "group": "Operations",
             "pages": [