feat: explainable activity log — reasons, subscriber names, snapshot gaps

The live activity feed flagged anomalies with no explanation and showed
opaque session keys. Make events self-describing and clickable.

- Clickable feed rows → read-only event-detail modal: humanized fields,
  entry/exit snapshots, and signed-chain provenance collapsed behind an
  audit disclosure (operator sees the story, auditor expands for crypto).
- Localized reason codes (backend i18n): the signed ledger now carries a
  stable REASON_CODE + params (+ English fallback) instead of free-text
  English. The UI translates via reason.<code> catalogs in sq/en, so an
  Albanian operator reads Albanian — from the same immutable event. Adding
  a language is a catalog change, no re-signing. (@parking/shared
  REASON_CODES, reasonPayload; entry/exit/subscription flows emit codes.)
- Subscriber-name resolution: a SUBSESS-… occurrence now shows the
  subscription holder's name (fallback "Abonent"/"Subscriber"). Resolved
  read-time server-side (events API + WS push) as a non-signed
  subscriberLabel; cached with invalidation on subscription edit/delete.
- Failed-snapshot visibility: a camera that was attempted but unreachable
  now shows a "⚠ camera unreachable" tile instead of a silent gap. The
  snapshots API returns failures[] from telemetry, filtered so a recovered
  capture shows no stale warning.

Claude-Session: https://claude.ai/code/session_01Xcm6ikLgGoCxxHrxtjkk5V

apps/web/src/lib/reason.ts

@@ -0,0 +1,22 @@
+import type { TFunction } from "i18next";
+import { REASON_CODES, type LedgerEvent } from "@parking/shared";
+
+// Localize a signed event's reason. The ledger signs a STABLE `reasonCode` (+ params)
+// plus an English `reason` fallback (see @parking/shared REASON_CODES). We translate
+// the code via the `reason.<code>` catalog so an Albanian operator reads Albanian and
+// an English operator reads English — from the SAME immutable event. Legacy events
+// (signed before reason codes existed) carry only `reason`, so we show that verbatim.
+
+const CODE_SET = new Set<string>(REASON_CODES);
+
+/** The localized reason sentence for an event, or null if it has no reason at all. */
+export function renderReason(payload: LedgerEvent["payload"], t: TFunction): string | null {
+  if (!payload) return null;
+  const code = typeof payload.reasonCode === "string" ? payload.reasonCode : null;
+  if (code && CODE_SET.has(code)) {
+    // i18next fills {{param}} from reasonParams; an absent key renders the raw token.
+    return t(`reason.${code}`, (payload.reasonParams ?? {}) as Record<string, unknown>);
+  }
+  // No code (legacy) or an unknown code (forward-compat) → the signed English fallback.
+  return typeof payload.reason === "string" ? payload.reason : null;
+}