v0.3.0 — chain inspector, an accessible lifecycle page, and a name for where you are

Ports the applicable parts of PGSimCity v0.7.2, v0.8.0 and v0.9.0.

Added

• Live version-chain inspector (from PG's v0.8.0 row-versions work): version chains now carry the real id of the transaction that wrote each version. Click the Record Version Towers and the info panel shows the busiest table's chain live — newest version in green, kept versions with the snapshot bound that still needs them, and versions below the OIT marked as garbage awaiting GC. Concurrent updates land in arrival order, so chains are honestly non-monotonic, just like the real engine.
• The life of a query (from PG's v0.9.0 observability view): the whole pipeline as an accessible, text-first page — sixteen stations from the client library to the committed record version and home again, keyboard-navigable, screen-reader friendly, no canvas required. Linked from the top bar.
• Close-range identification (from PG's v0.7.2): zoom in past 1.45× and a chip names the building at the screen center — "You are at: Execution Hall · EXE".
• Trademark & independence notice (from PG's v0.8.0): README, About panel and the lifecycle page now state that FBSimCity is an independent educational project; Firebird® is a registered trademark of the Firebird Foundation Incorporated.

Changed

• Camera zoom limits consolidated into single constants — one set of numbers to blame for any zoom-related disorientation.
• Table version chains are seeded with transaction ids well below the initial markers, so the inspector's garbage labels are meaningful from the first minute.

Deliberately not ported

• PG's v0.9.0 measurement/telemetry system. FBSimCity makes no network calls and keeps it that way.
• Tour-advances-on-user-input — FBSimCity's tour has always worked that way.
• WAL responsiveness fixes — Firebird has no WAL; the excavation's careful writes remain the whole point.