fix(landing): compare pages and pricing describe what ships today - #2348

🟡 Confidence 6/10 · needs attention. Held at 6 because a correctness warning is open.
_{1 warning −1 · tests not needed · risk low}

Rewrites the landing compare, pricing and alerting copy in en, ja and ko so it matches what ships today: uptime checks, on-call, SLOs, ten alert destinations, the one-container self-host and the real retention tiers. Three row verdicts change. Safe to merge.

• Compare rows now credit Maple with uptime checks, on-call, SLOs and ten alert destinations
• Self-host copy describes the one-container image with no alerting, matching the self-host docs
• Retention copy states 30 days for traces and logs, 90 for metrics, 12 months for service charts
• cmp_sn_channels_maple and cmp_hc_slo_maple rows move from competitor to even

Still open from earlier reviews

• 🟠 Warning · F3 · SigNoz page still promises a bring-your-own ClickHouse self-host · apps/landing/messages/en.json:1186

_{8078dd5 · Reply "won't fix" to dismiss a finding, or mention @maple-review-bot to ask about one.}