gargoyle-firewall-util: fix weekly-range restriction rules never loading

[ispyisail]

Summary

• Two independent bugs in make_nftables_rules.c meant every restriction/whitelist rule using the "weekly" schedule type (the general Restrictions form's own long-existing option, not just the Family Time wizard) silently failed to load into nftables — enabled in UCI, no error surfaced anywhere, just never enforced.
• timerange weekly-ranges → the nft timerange extension's own grammar (command-line parser and its own display output) is weeklyranges, one word.
• Even with the keyword fixed, a standalone space-surrounded - token in the value (the canonical Day HH:MM - Day HH:MM display format weekly_i18n() needs to correctly localize day names) gets misread by nft's own CLI as an attempted option flag.
• Fixed by sanitizing a copy of the value (collapsing - to -, reusing the dynamic_replace loop idiom already established in restore_quotas.c for the same class of problem) before it reaches the nft command line, and correcting the keyword — the display format itself is unchanged.

Test plan

• Scoped compile: make package/gargoyle-firewall-util/{clean,prepare,compile} — clean, no new warnings
• Verified live on real hardware (GL-MT6000): hand-constructed the exact nft command the fixed binary produces, confirmed it loads; confirmed the old binary reproducibly fails with the exact syntax error seen in the wild
• vnet phase 65 (new): real end-to-end packet test — a weekly-range rule covering the router's current day/time genuinely blocks a client's traffic, the identical rule shifted off-window genuinely allows it. All 3 checks pass.