chore(contracts): record testnet deployment (#1020)

* chore(contracts): record testnet deployment

Deploys the registry and demo-emitter contracts to Stellar testnet via
deploy/deploy_testnet.sh and commits the resulting contract IDs and wasm
hashes. This is what flips CI's verify-provenance job from skip to a real
check, and what apps/web's fireDemoEvent.ts needs to stop returning
DemoEmitterNotConfiguredError on the /demo/contracts "Fire test event"
button.

registry:     CCM4U5BGSLAGD2OYHAQUYLXVZNWI4EECJYPVJMOBSYI434FZ5Z2LGIWO
demo-emitter: CAP6TJP7WVVSAK5BKKAA32J6G7RPT6X6Q7US7SMBGZ3NZ73HSXFNFCRH

Both wasm hashes verified against on-chain state via `stellar contract
fetch` before committing.

* fix(contracts): redeploy with a reproducible build, matching CI's rebuild

The first deployment (939be5ae.../e16bedfd...) redeployed here was built
locally without CARGO_HOME normalization: soroban-sdk's ledger.rs embeds
its own absolute source path via a panic-location capture, so the wasm
hash differed by build machine even with identical source and identical
rustc version. verify-provenance's independent rebuild in CI (CARGO_HOME=
/home/runner/.cargo) correctly caught the drift and failed.

Rebuilt with RUSTFLAGS="--remap-path-prefix=$CARGO_HOME=/home/runner/.cargo"
to match CI's embedded path exactly, confirmed the local build hash equals
CI's independently-rebuilt hash, and redeployed both contracts from that
exact wasm.

registry:     CDSCV5WBIK74OXFQLJMBMJHBWYBNEFGQGEG2YBKVKJSIWKP676AJF2QA
demo-emitter: CBWXJ3AJZ7Y57XZWZV75VZRRSCZ5DT5VLPKKSC6FYG4YI4ELO5AXBBVP

---------

Co-authored-by: Salmatcre8 <118213044+Salmatcre8@users.noreply.github.com>

Author: determined-001

contracts/deployed.testnet.json

@@ -1,15 +1,15 @@
 {
   "network": "testnet",
-  "deployerPublicKey": "<RUN contracts/deploy/deploy_testnet.sh TO POPULATE>",
-  "deployedAt": "",
+  "deployerPublicKey": "GBBHYIMKT43UAFUG2F4QHSJK25Q2AZSA3RRB6JSHUABDAXMQARGJZYHG",
+  "deployedAt": "2026-08-11T19:31:21Z",
   "contracts": {
     "registry": {
-      "contractId": "<POPULATED BY deploy_testnet.sh>",
-      "wasmHash": ""
+      "contractId": "CDSCV5WBIK74OXFQLJMBMJHBWYBNEFGQGEG2YBKVKJSIWKP676AJF2QA",
+      "wasmHash": "939be5ae7d6b6c421f30dad75c56e613c5136897aadf54dfec2a7ae441cec334"
     },
     "demoEmitter": {
-      "contractId": "<POPULATED BY deploy_testnet.sh>",
-      "wasmHash": ""
+      "contractId": "CBWXJ3AJZ7Y57XZWZV75VZRRSCZ5DT5VLPKKSC6FYG4YI4ELO5AXBBVP",
+      "wasmHash": "e16bedfd9616c5653bcefcafa5b055f0befabd7891a8d8350a14f78fba578757"
     }
   }
 }