refactor(http): drop deprecation-stub routes from the migrated dashboard / entities / events surface

[AquiGorka]

Follow-up to #106.

Summary

PR #106 migrated every dashboard / entities / events route to the per-PP /api/v1/providers/:ppPublicKey/... shape and left 410 Gone stubs at the old un-scoped paths so callers could migrate. The migration is settled and no caller in any consumer repo still hits the un-scoped paths, so the stubs are dropped — the router now answers 404 (route not found) for those URLs.

What changes

• Delete the 16 deprecation stubs:
  • 14 in src/http/v1/dashboard/routes.ts (POST /dashboard/pp/delete, GET /dashboard/{channels,mempool,operations,treasury,utxos,transactions,transactions/:id,bundles/:id,audit-export,metrics,council/membership}, POST /dashboard/council/{join,membership})
  • POST /entities (un-scoped) — the entire src/http/v1/entities/routes.ts becomes empty and is deleted
  • GET /events/ws (un-scoped) — the entire src/http/v1/events/routes.ts becomes empty and is deleted
• Remove the buildEntitiesRouter + buildEventsRouter imports and mounts from src/http/v1/v1.routes.ts.
• Remove the orphan deprecation comment block + the sibling already-bare-deleted-routes note in src/http/v1/dashboard/routes.ts.
• Remove the three integration tests that asserted the 410 behavior of the deleted stubs (bundle-admin.test.ts, dashboard-metrics.test.ts, events-ws.test.ts).
• Bump version to 0.7.3.

The live per-PP handlers (dashboard/*.ts, entities/post.ts, entities/challenge.ts, events/ws-handler.ts) are unchanged and stay mounted via providers/routes.ts.

Test plan

• deno fmt --check clean
• deno lint clean
• deno task test:unit — 64 passed / 0 failed
• deno task test:integration — 96 passed / 0 failed (99 → 96 is the 3 deleted 410-stub tests, no regressions)
• Curl every old path against a locally-running build — all 16 return 404 (not 410)
• Curl per-PP replacement paths (channels, metrics, treasury, entities) — all respond live (401 from jwtMiddleware on the protected ones; the public entities POST hits requirePpExists and answers Provider not found)
• Grep all consumer repos (provider-console, council-console, network-dashboard, network-dashboard-platform, moonlight-pay, browser-wallet, moonlight-sdk, local-dev) — zero non-test call sites on any of the 16 deleted paths