Add Import from Schematic Image feature

[esaruoho]

Summary

• Adds File > Import from Schematic Image... menu item
• Users can upload/drop a schematic photo, screenshot, or scan
• Calls Google Gemini Vision API directly from the browser (no server needed) to convert the image to CircuitJS1 text format
• Shows image preview, analysis status, and generated circuit text before importing
• API key stored in localStorage with masked display and change button
• Error handling for invalid key, rate limits, network errors, oversized images

New file

• ImportFromSchematicDialog.java — dialog with image picker, JSNI Gemini API call, and import button (follows ImportFromDropboxDialog pattern)

Modified files

• Menus.java — added menu item field and File menu entry
• CommandManager.java — added command dispatch

Test plan

• Build with gradle compileGwt
• Verify File menu shows "Import from Schematic Image..."
• Click menu item, select a PNG of a simple circuit
• Enter Gemini API key when prompted, verify it persists in localStorage
• Click Analyze, verify circuit text appears
• Click Import Circuit, verify circuit loads and simulates
• Test error cases: no API key, invalid key, no image, large file (>10MB)
• Test Change button updates the stored API key

Generated with Claude Code