Clipboard copy works in non-secure contexts

Fixed

• Copy (card copy button, context-menu Copy, ShareDialog copy-link) silently failed when the app was opened over a LAN IP on http (e.g. Chromium on Linux), because navigator.clipboard requires a secure context. Added lib/clipboard.ts copyText() with an execCommand fallback and routed all text-copy paths through it.

Notes

• Image-card copy (ClipboardItem) and context-menu Paste still need a secure context (no non-secure fallback exists); Ctrl/Cmd+V paste works everywhere.