refactor: extract magic constants — wave 3 (font lifecycle)

Promote font-loading scheduling and lifecycle tunables to named
module-level constants:

- comparisonStore: FONT_READY_FALLBACK_MS (1000ms) — UI unblock safety net
- fontLifecycleManager:
  - PURGE_INTERVAL_MS (60000) — periodic eviction sweep
  - IDLE_CALLBACK_TIMEOUT_MS (150) — requestIdleCallback timeout
  - SCHEDULE_FALLBACK_MS (16) — setTimeout fallback (~60fps)
  - YIELD_INTERVAL_MS (8) — parse-loop yield budget for non-Chromium
  - CRITICAL_FONT_WEIGHTS ([400, 700]) — data-saver allowlist
- FontEvictionPolicy: DEFAULT_FONT_TTL_MS (5 minutes)
- FontLoadQueue: FONT_LOAD_MAX_RETRIES (3)

No behavior changes — values preserved exactly. Class-private fields
that mirrored these constants are removed in favor of module scope.

src/entities/Font/model/store/fontLifecycleManager/utils/fontEvictionPolicy/FontEvictionPolicy.ts

@@ -1,6 +1,11 @@
+/**
+ * Default TTL after which an unpinned font is eligible for eviction.
+ */
+export const DEFAULT_FONT_TTL_MS = 5 * 60 * 1000;
+
 interface FontEvictionPolicyOptions {
     /**
-     * TTL in milliseconds. Defaults to 5 minutes.
+     * TTL in milliseconds. Defaults to {@link DEFAULT_FONT_TTL_MS}.
      */
     ttl?: number;
 }
@@ -17,7 +22,7 @@ export class FontEvictionPolicy {
 
     readonly #TTL: number;
 
-    constructor({ ttl = 5 * 60 * 1000 }: FontEvictionPolicyOptions = {}) {
+    constructor({ ttl = DEFAULT_FONT_TTL_MS }: FontEvictionPolicyOptions = {}) {
         this.#TTL = ttl;
     }