fix(erd): large diagrams fit, Ctrl/Cmd++ zooms, Esc closes the search before the pick (#1154)

[ZhuchkaTriplesix]

Closes #1154

What was wrong

• Fit did not fit large diagrams. The fit zoom was clamped to the 20 % minimum, so a schema of 150–200 tables opened partly outside the viewport.
• Ctrl/Cmd++ did nothing. Only Ctrl/Cmd+= was bound; + is Shift+= on most layouts.
• Esc never closed the search. QueryaSearchField handles Esc itself (clear the text, then drop the focus), so the view's Esc binding never ran. The panel stayed open and the canvas lost the keyboard: zoom and search shortcuts stopped working until a click.
• Closing the search would clear the pick. The view's Esc closed the search and cleared the selection in one go, so a table found with Enter lost its highlight as soon as the search was closed. The search also stayed open after a pick.
• Clicks did not give the keyboard back. Clicking a card or the empty canvas did not focus the canvas.
• Hiding the picked table left every card faded, because the pick pointed at a table no longer drawn.

Changes

• ErdLayout.fitScale: the fit may go below 20 %; the viewer's minimum zoom follows it.
• Ctrl/Cmd+Shift+= and the + key zoom in.
• Picking from the search (Enter or click) centres and selects the table, closes the search and focuses the canvas.
• An empty search that loses the focus closes and focuses the canvas. Esc on the canvas closes an open search first, then clears the pick.
• A click on a card or the canvas focuses the canvas. Hiding the picked table clears the pick.
• Tests: fit below 20 % (unit and widget), Ctrl+Shift+= zooms in, Enter in the search picks and closes it, Esc with an open search keeps the pick and the next Esc clears it.