Bump link-cache to 0.5.0 and migrate to owned link-cache.jsonc

[chalin]

• Bumps link-cache 0.3.0 -> 0.5.0, skipping 0.4.x, so the owned-cache format migration lands with the bump (precedents: Switch the committed link cache to owned JSONC (link-cache.jsonc) chalin/docsy-starter#23 for the migration, Bump link-cache to ^0.5.0 (status→result cache schema) chalin/docsy-starter#25 for the 0.5.0 bump).
• Ships the imported link-cache.jsonc (89 entries, all 200, timestamps preserved, entries not re-checked) so CI's drift check stays green; .lycheecache becomes a derived, gitignored file and the drift-check hint names the new file.
• Notes that 0.5.0 turns staleness checks off by default (CI verifies only uncached URLs): no scheduled refresh lane exists here; the follow-up is unscheduled.
• Rounds lychee.toml max_cache_age from 375d to 365d.