Add BitSquiggle visualization to every master-fingerprint display

[schnuartz-ai]

Summary

• Adds a compact BitSquiggle32 visualization next to every place SeedSigner shows a BIP-32 master fingerprint, so it can be compared by eye against the same fingerprint shown in a companion wallet app (or another SeedSigner screen) instead of matching 8 hex characters one by one.
• The BitSquiggle32 core (a reversible 32-bit mixer + connection-graph renderer, pure Python/no new dependencies) is vendored unmodified into src/seedsigner/helpers/bitsquiggle32.py, under its original "Grug 2-Clause License" (permissive, see the upstream repo). A small adapter in src/seedsigner/helpers/bitsquiggle.py renders it to a pixel-exact, nearest-neighbor-scaled PIL image, sized to fit whatever space is actually free on each screen.

Screens covered

1. SeedFinalizeScreen ("Finalize Seed") — inline next to the fingerprint, group re-centered as a unit
2. SeedOptionsScreen (per-seed menu) — appended after the top-nav title
3. SeedExportXpubDetailsScreen ("Xpub Details") — inline next to the left-aligned fingerprint row
4. ToolsAddressExplorerAddressTypeScreen ("Address Explorer") — inline next to the left-aligned fingerprint row
5. ToolsCalcFinalWordDoneScreen (12th/24th word tool) — centered group, same layout as Create online build instructions (without needing a 2nd Pi) #1
6. MultisigWalletDescriptorScreen ("Descriptor Loaded") — one squiggle per cosigner, shown as a row below the existing hex text; falls back to text-only if there isn't at least one native-size row of vertical room (e.g. 5+ cosigners wrapping the hex text to 3 lines)
7. SeedReviewPassphraseScreen ("Verify Passphrase") — replaces the {before} >> {after} hex text with two squiggles and a >> separator, since there wasn't room for both the long combined hex string and squiggles side by side

Screenshots

Rendered via the repo's own screenshot-generator hardware mocks (ScreenshotRenderer). Included in this branch under docs/pr-screenshots/bitsquiggle/ for review — illustrative only, not part of the app, fine to drop before merge.

1. Finalize Seed

2. Seed Options (per-seed menu)

3. Xpub Details

4. Address Explorer

5. 12th/24th Word tool

6. Multisig Descriptor Loaded (one squiggle per cosigner)

7. Verify Passphrase (before >> after)

Test plan

• pytest tests/test_flows_seed.py tests/test_flows_tools.py tests/test_seed.py — 33/33 pass, unchanged
• Each screen manually rendered via the screenshot-generator mocks and reviewed independently against its own screenshot for placement/sizing issues; two centering issues and one real overlap bug (multisig row's size floor could overlap the button list when the cosigner list wraps to 3 lines) were found this way and fixed
• Manually stress-tested the longest translated "fingerprint" labels currently in seedsigner-translations (German, Russian) on the original finalize-screen placement to confirm the layout doesn't clip
• Not yet tested on real hardware (only via the screenshot-generator's mocked renderer)

🤖 Generated with Claude Code

[newtonick]

@schnuartz-ai can you post an actual screenshot to help the review process?