Clipboard: HTTP-safe fallback for copy actions

[Panthevm]

Summary

• On non-secure origins (plain HTTP) navigator.clipboard is undefined, so every Copy action in the UI threw Cannot read properties of undefined (reading 'writeText') — reproducible in DB Console → Result → Copy as JSON / Markdown.
• Add src/utils/clipboard.ts with a copyToClipboard(text) helper that prefers navigator.clipboard.writeText and falls back to a Range/Selection-based path. The fallback installs a capture-phase copy listener with stopImmediatePropagation so CodeMirror's own copy handler can't overwrite clipboardData (otherwise it was copying whatever line was focused in the SQL editor). Selection via Range also avoids Radix DropdownMenu's FocusScope yanking focus back to the trigger.
• Replace all direct navigator.clipboard.writeText callers: db-console result export (3 sites), ResourceBrowser query bar, claude-chat element picker & badge, ViewDefinition materialized-view toast, notebooks share URL.

Test plan

• DB Console over HTTP: run a query, Copy as JSON → pasted text equals the JSON, not the focused SQL line.
• DB Console over HTTP: Copy as Markdown and "Copy all as …" with multiple results.
• DB Console over HTTPS: same actions still use the native navigator.clipboard path.
• ResourceBrowser: copy current query URL.
• ViewDefinition: materialize a view, copy the view name from the toast.
• Claude chat element picker + badge: copy element context.
• Notebooks: share notebook URL.