feat: create comprehensive specs for all four capabilities

- line-deletion: keyboard shortcuts and bulk delete with confirmation
- label-management: full CRUD UI in sidebar with search/filter
- docker-deployment: multi-stage build, compose, health checks
- hacker-theme: matrix-style colors, neon glows, monospace fonts

openspec/changes/enhance-annotation-features-and-deployment/specs/line-deletion/spec.md

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+## ADDED Requirements
+
+### Requirement: Delete selected line with keyboard
+The system SHALL allow users to delete the currently selected line annotation using keyboard shortcuts (Delete key or Backspace key).
+
+#### Scenario: Delete selected line with Delete key
+- **WHEN** a line is selected (selectedLineId is set) and user presses Delete key
+- **THEN** system sends DELETE request to `/api/annotations/{id}`, removes line from display, clears selection state, and triggers annotation refresh
+
+#### Scenario: Delete selected line with Backspace key
+- **WHEN** a line is selected and user presses Backspace key
+- **THEN** system sends DELETE request to `/api/annotations/{id}`, removes line from display, clears selection state, and triggers annotation refresh
+
+#### Scenario: No line selected when pressing delete
+- **WHEN** no line is selected (selectedLineId is null) and user presses Delete or Backspace key
+- **THEN** system takes no action and does not make any API calls
+
+#### Scenario: Delete key during line drawing
+- **WHEN** user is actively drawing a line (drawingLine state is not null) and presses Delete key
+- **THEN** system cancels the line drawing operation but does NOT delete any existing lines
+
+### Requirement: Delete all lines with confirmation
+The system SHALL provide a UI button in the Toolbox to delete all line annotations at once with user confirmation.
+
+#### Scenario: User clicks Delete All Lines button
+- **WHEN** user clicks "Delete All Lines" button in Toolbox
+- **THEN** system displays a confirmation dialog with message "Delete all line annotations? This cannot be undone." and Cancel/Confirm buttons
+
+#### Scenario: User confirms delete all lines
+- **WHEN** confirmation dialog is open and user clicks Confirm button
+- **THEN** system sends DELETE request to `/api/annotations?type=line`, removes all lines from display, clears selection state, triggers annotation refresh, and closes dialog
+
+#### Scenario: User cancels delete all lines
+- **WHEN** confirmation dialog is open and user clicks Cancel button
+- **THEN** system closes dialog without making any API calls or removing any lines
+
+#### Scenario: No lines exist when clicking delete all
+- **WHEN** user clicks "Delete All Lines" button and no line annotations exist in database
+- **THEN** system still shows confirmation dialog (user confirms/cancels normally)
+
+### Requirement: API support for bulk line deletion
+The API SHALL support deleting multiple annotations by type via query parameters.
+
+#### Scenario: Delete all lines via API
+- **WHEN** DELETE request sent to `/api/annotations?type=line`
+- **THEN** system deletes all annotations where label_type equals 'line' and returns `{ success: true, deleted: <count> }`
+
+#### Scenario: Delete all annotations via API
+- **WHEN** DELETE request sent to `/api/annotations?all=true`
+- **THEN** system deletes all annotations regardless of type and returns `{ success: true, deleted: <count> }`
+
+#### Scenario: Invalid type parameter
+- **WHEN** DELETE request sent to `/api/annotations?type=invalid_type`
+- **THEN** system returns 400 error with message "Invalid annotation type"
+
+### Requirement: Delete button in Toolbox
+The Toolbox SHALL display a "Delete All Lines" button when line annotations exist.
+
+#### Scenario: Lines exist in database
+- **WHEN** one or more line annotations exist in the database
+- **THEN** Toolbox displays "Delete All Lines" button in destructive styling (red theme)
+
+#### Scenario: No lines exist
+- **WHEN** no line annotations exist in database
+- **THEN** Toolbox displays "Delete All Lines" button in disabled state with reduced opacity
+
+#### Scenario: Button position in Toolbox
+- **WHEN** Toolbox renders
+- **THEN** "Delete All Lines" button appears below the color picker section and above the "Delete" tool button