[Enhancement]: [P3] Optionally recognize TDT-imported original towers as Founding towers

Narrowed from the original founder-recognition scope after the no-appVersion save case shipped (PR #633).

Shipped: markFounderFromLoadedFile (src/engine/sim/founderStatus.ts) now promotes any tower loaded from a real save FILE or localStorage slot with no appVersion stamp to Founder (wired into SaveGame.loadResult/loadSlot/import). This recovers genuine pre-v1.23.0 towers (which predate the appVersion stamp) — including the owner's flagship towerone saves. It lives at the load boundary, not in deserialize, so an in-session undo/redo snapshot (also stamp-free) can't flip a brand-new 2.0 tower to Founder. Verified against 14 real owner saves plus the leakage cases (new game stays non-founder; a post-2.0 import is not stamped founder unless it carries the earned flag).

Remaining (this issue): a TDT-imported original SimTower tower (src/game/saveLoad.ts binary import) synthesizes a save with no appVersion, and is deliberately NOT auto-founded, because importing a 1994 tower into 2.0 is arguably founding a new tower rather than loading a pre-2.0 Verticopolis save. Decision needed: should the "most founding" towers of all carry the badge? If yes, call markFounderFromLoadedFile on the TDT import path too. Low priority / product judgment.

Start with src/game/saveLoad.ts and trace the TDT binary import path, then compare it with markFounderFromLoadedFile in src/engine/sim/founderStatus.ts and the existing SaveGame load wiring. The remaining work depends on deciding whether an imported original SimTower tower counts as a founding tower; done means that product decision is reflected consistently in the import behavior.