Liquid signing aborts for asset tickers longer than 7 characters

Signing a Liquid transaction containing a registered asset with a ticker of 8 or more characters causes Jade to display:

> Internal error
> sign_tx.c:135

The device then restarts.

## Environment

- Hardware: Jade Plus (`JADE_V2`)
- Features: `DEV`
- Firmware: `1.0.40-111-gcfce08ce`
- Commit: `cfce08ced9f58ed0244e516f1d7f0c61a82889ee`
- ESP-IDF: `v5.5.4`

This commit is the current `master` at the time of reporting.

## Steps to reproduce

1. Build and install `master` for `jade_v2`.
2. Initiate a Liquid `sign_tx` operation containing a registered asset whose ticker is at least 8 characters long.
3. Allow Jade to display the asset output or asset summary.
4. Jade aborts at `main/ui/sign_tx.c:135` and restarts.

Examples already present in the generated asset registry include:

- `TREETEST` — 8 characters
- `Sangiovese2` — 11 characters
- `TEST-COLLECTION3` — 16 characters

## Cause

Ticker display buffers are declared as:

```c
char ticker[8];
```

## Reproduction test data

```json
{
"description": "Liquid issuance with a valid ELIP-0100 contract whose ticker is exactly 8 bytes",
"input": {
"network": "testnet-liquid",
"txn": "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",
"asset_info": [
{
"asset_id": "3d076db396b99cf0ac2284f5b10ff572aa737eacf40730d338f0ec697a5459f7",
"contract": {
"entity": {
"domain": "lending.example"
},
"issuer_pubkey": "0250929b74c1a04954b78b4b6035e97a5e078a5a0f28ec96d547bfee9ace803ac0",
"name": "simplicity-lending/v1 c229fe57de9a0ce287bb518fbe3bb05e41b79c0940d5a9577aee286c664d3495:0",
"precision": 0,
"ticker": "SLFc229f",
"version": 0
},
"issuance_prevout": {
"txid": "c229fe57de9a0ce287bb518fbe3bb05e41b79c0940d5a9577aee286c664d3495",
"vout": 0
}
}
],
"trusted_commitments": [null, null, null],
"change": [null, null, null],
"inputs": [{}]
},
"expected_output": [""]
}
```

Start in main/ui/sign_tx.c at the failure reported on line 135 and inspect the ticker display buffers declared as char ticker[8]. Use the provided Liquid sign_tx reproduction data and the longer registry tickers to verify the failure. Done means assets with tickers of 8 or more characters can be displayed and signed without an internal error or device restart.

Written by the indexing model from the issue text.