Improve config UI editing, language binding, and import feedback

[afffe18]

Motivation

• Make configuration editing more user-friendly by splitting complex JSON blobs (annotations, colored areas) into per-item form controls with add/remove, and add removal controls for repeated instances.
• Ensure plot text fields (frame title, legend title, axis labels) follow the selected plot language so editing matches the displayed language.
• Provide clear feedback for database imports and derive axis/column options from imported metadata to streamline importing .xlsx or Teable sources.
• Align exported JSON keys to the documented reference schema (config_explanation.jsonc) so the produced config matches external expectations.

Description

• Replaced raw JSON textareas for annotations and colored areas with structured per-item form fields and add/remove buttons in src/App.tsx.
• Added remove controls (✕) for dataframes, frames, axes, layers, guidelines, annotations and colored areas, including safe axis removal handling, and switched layer name editing to a dropdown derived from imported columns.
• Implemented database import flow with importDatabase, availableColumns state, parseColumnsFromImportResult and getAxisBasesFromColumns to call /api/import-database for both Teable and file uploads and populate axis / layer options accordingly in src/App.tsx.
• Mapped internal PlotConfig to the snake_case / reference-style external schema via toExternalConfig and updated exportConfig to emit the reference-style JSON in src/utils/configIo.ts, and adjusted visible jsonPath labels across the UI.

Testing

• Ran a production build with npm run build, which executed tsc -b and vite build, and the build completed successfully.
• No automated unit tests are present in the repository, so validation focused on TypeScript compilation and the Vite production build which both succeeded.

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Codex Task