feat(inline-edit): add WYSIWYG inline dashboard editing mode

Replace the disconnected board edit page with inline editing directly
on the board view. Toggle with Ctrl+E or the Edit button. Features:

- Edit mode store with changeset accumulation and batch save
- Floating toolbar (save, discard, add section, board settings, exit)
- Widget hover overlays with edit/delete/drag controls
- Type-specific widget config panels for all 14 widget types
- Section inline editing (title, icon picker, delete)
- "+" buttons for adding widgets and sections inline
- Section-level drag-and-drop reordering via svelte-dnd-action
- Batch save API endpoint (single Prisma transaction)
- Board properties side panel with live theme/wallpaper preview
- Modal widget type picker with search filtering
- Icon picker component with visual grid and search
- Confirmation dialog modal for all destructive actions
- HTML format support for Note widget (in addition to markdown/text)
- Full i18n support (en + ru) for all new UI strings
- Legacy edit page banner linking to new inline mode

plans/inline-dashboard-editing/phase-1-edit-mode-state.md

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+# Phase 1: Edit Mode State Infrastructure
+
+**Status:** ⬜ Not Started
+**Parent plan:** [PLAN.md](./PLAN.md)
+**Domain:** frontend
+
+## Objective
+Create the foundational edit mode state management and toggle mechanism that all subsequent phases build upon.
+
+## Tasks
+
+- [ ] Create `src/lib/stores/editMode.svelte.ts` with state: `{ active, boardId, dirty, changeCount }`
+- [ ] Export functions: `enterEditMode(boardId)`, `exitEditMode()`, `markDirty()`, `resetDirty()`
+- [ ] Add "Edit Mode" toggle button to `BoardHeader.svelte` (replaces the current "Edit" link to `/boards/[id]/edit`)
+- [ ] When toggled ON: set edit mode active, show visual indicator (subtle board border glow or tint)
+- [ ] When toggled OFF: if dirty, show confirmation dialog "Discard unsaved changes?"
+- [ ] Register keyboard shortcut `Ctrl+E` / `Cmd+E` to toggle edit mode
+- [ ] Pass edit mode state as Svelte context from board view page
+- [ ] Add `editMode` context consumer helpers for child components
+- [ ] Visual indicator: board gets a subtle colored top-bar or border when in edit mode
+
+## Files to Modify/Create
+- `src/lib/stores/editMode.svelte.ts` — new store
+- `src/lib/components/board/BoardHeader.svelte` — replace Edit link with toggle button
+- `src/routes/boards/[boardId]/+page.svelte` — provide edit mode context, visual indicators
+
+## Acceptance Criteria
+- Clicking the toggle enters/exits edit mode
+- Ctrl+E toggles edit mode
+- Board view page visually indicates edit mode is active
+- Child components can read edit mode state via context
+- Dirty state tracking works (increments on markDirty, resets on save/discard)
+
+## Notes
+- Use Svelte 5 runes ($state, $derived) for the store
+- The keyboard shortcut must not conflict with existing shortcuts
+- Guest users / users without edit permission must NOT see the toggle
+
+## Review Checklist
+- [ ] All tasks completed
+- [ ] Code follows project conventions
+- [ ] No unintended side effects
+- [ ] Build passes
+- [ ] Tests pass (new + existing)
+
+## Handoff to Next Phase
+<!-- Filled in after completing this phase -->