docs: Stellar multisig stealth withdrawal guide (#53)

- Add guides/stellar-multisig-withdrawal.mdx covering multisig primer,
  N-of-M signature coordination, SDK primitives usage, recovery scenarios,
  and a worked 3-of-5 end-to-end example targeting futurenet
- Register page in docs.json under Guides > Operations
- Add cross-link from sdk/chains/stellar.mdx See Also section
- Add cross-link from guides/privacy-best-practices.mdx See Also section

Closes #41

Author: baedboibidex-cmyk

docs.json

@@ -118,6 +118,14 @@
               "guides/single-chain-agent",
               "guides/multichain-agent",
               "guides/bring-your-own-model",
+              "guides/privacy-best-practices"
+            ]
+          },
+          {
+            "group": "Operations",
+            "pages": [
+              "guides/stellar-mainnet-deployment",
+            "guides/stellar-multisig-withdrawal"
               "guides/privacy-best-practices",
               "guides/spectre-stellar-cookbook",
               "guides/stellar-federation",

guides/privacy-best-practices.mdx

@@ -170,4 +170,8 @@ Identical amounts create a fingerprint. Consider varying the amount.
 | Vary payment amounts slightly | Prevents amount-based fingerprinting |
 | Use different times of day | Avoids timezone-based profiling |
 | Consolidate stealth addresses periodically | Reduces on-chain footprint |
+
+## See Also
+
+- [Stellar Multisig Stealth Withdrawals](/guides/stellar-multisig-withdrawal) — additional coordination and recovery considerations for multisig source accounts
 - [Stellar Offline Transaction Signing](/guides/stellar-offline-signing) — keep stealth spending keys fully air-gapped using the offline signing workflow