fix(frontend): dashboard audit polish — inspector defaults, empty states, OSS theme toggle

- Default actor tab is State (Workflow for workflows); Database only leads for
  raw-SQLite actors. The dashboard now canonicalizes the tab order advertised
  by the runner's inspector bundle so older runners get the same order.
- Database tab: user tables first, _rivet_* tables grouped under "Internal",
  and the first user table is selected by default.
- Connections tab: table (ID, type, hibernatable, params, state) with a proper
  empty state instead of a raw object tree; Queue empty state matches Schedules.
- Metadata: Key rendered as copyable mono text instead of a JSON tree.
- OSS top bar gets a light/dark toggle (cloud keeps it in the user menu).
- ?n=counter (plain string) no longer renders a Zod error page.
- Provider/runner copy no longer references Rivet Cloud in OSS; settings drawer
  description is flavor-aware; Live badge uses primary instead of destructive.
- "No more Actors to load." only shows after more than one page.

Amp-Thread-ID: https://ampcode.com/threads/T-01a072ad-3c9e-744e-b4b9-a8997aae8809
Co-authored-by: Nicholas Kissel <nicholas@rivet.gg>

Author: ampagent