Add bulk actions for data mappings

[ousamabenyounes]

Closes #505.

Summary

• Add page-level selection and bulk Confirm/Reject controls for proposed mappings.
• Reuse the existing per-mapping decision API so each selected row keeps its own audit record.
• Wait for every row request, refresh after partial failures, and retain only still-proposed failed selections for retry.
• Clear selection when the knowledge base, page, query, status, or tab changes, with distinct accessible labels in English and Chinese.

Test verification (RED → GREEN)

• RED: on unmodified dev, the focused contract fails because bulk decision helpers, stale-selection filtering, and localized checkbox labels do not exist.
• GREEN: all four focused mapping tests pass, including exactly-once per-row calls and waiting for every request before reporting a partial failure.
• Fix-revert RED: restoring early Promise.all rejection, stale-ID submission, and ambiguous labels produces three targeted failures.
• Full local suite: migrations ran twice; formatting, workspace clippy/tests/build, required database-backed store tests, 12/12 web tests, typecheck, style guard, and the production web build passed. The full web suite and build passed again after rebasing onto current dev.

Validation

• Source-map-backed Chromium V8 measurement covered 127/127 changed executable production lines with zero uncovered.
• A real Vite UI, Rust backend, pgvector database, and Chromium exercised select-all on/off, row select/deselect, disabled bulk selection during an unresolved individual decision, a forced partial bulk failure with retained-row retry, bulk Confirm, and bulk Reject.
• The database finished with two confirmed and two rejected mappings and exactly four matching per-row mapping.decided audit records.
• Independent Codex functional and strict engineering-rule reviews accepted the final rebased diff.