feat(webui): add regex filter help modal with usage examples

[123hi123]

Summary

• Replaced the tooltip-only ℹ️ icon next to the regex filter input with a clickable icon that opens a help modal
• The modal explains the AND logic (multiple regex lines must ALL match — a common pitfall) and the node tag format (<SubscriptionName>/<NodeName>)
• Includes a table of common usage patterns with examples:
  • my_sub/.* — match all nodes from a subscription
  • (sub1|sub2)/.* — match nodes from multiple subscriptions (OR)
  • .*/.*香港.* — match nodes whose name contains a keyword
  • ^sub/exact-node$ — match a specific node exactly
• Applied to both the create form (PlatformPage) and the edit form (PlatformDetailPage)
• Added zh-CN / en-US translations for all new strings

Motivation

Users often set multiple regex lines expecting OR behavior, but Resin uses AND logic — a node must match all lines to be routable. The existing tooltip was too subtle; a dedicated help modal makes this much clearer.

Test plan

• Open Platforms → Create → click ℹ️ next to regex input → verify modal appears with correct content
• Open a platform detail → Config tab → click ℹ️ → verify same modal
• Click outside modal or "关闭" button → verify modal closes
• Switch to English → verify translations

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