Meyd-908 🎁

h3. Tasks * FE‑1: BulkTagButton component * FE‑2: BulkTagModal component * BE‑1: Bulk‑tags endpoint + permission guard * DB‑1: Index on contact_id/tag_id * Test‑1: Unit + integration + Cypress E2E * Docs‑1: Help article & release notes * Ops‑1: Feature flag, monitoring, logs

h3. Acceptance Criteria # Toolbar displays a “Bulk Tag” button for users with the BulkTag permission. # Users can select multiple contacts (checkboxes, shift‑click). # Clicking the button opens a modal with a searchable multi‑select dropdown for tags. # “Apply” sends a single API request: POST /api/v1/contacts/bulk-tags. # Success toast shows count and an Undo link (available 10 s). # Partial failures display a detailed error overlay. # All interactions are keyboard‑accessible and screen‑reader friendly. # Analytics events `feature_meYD_908_open`, `feature_meYD_908_apply_success`, `feature_meYD_908_apply_error`, `feature_meYD_908_undo` are emitted. MEYD-908

h3. Description *Problem*: Users must tag contacts one‑by‑one, which is time‑consuming. *Solution*: Introduce a bulk‑tag UI (toolbar button → modal) that lets users select multiple contacts and apply one or more tags in a single operation. # Success toast shows count and an Undo