[Story]: Jira CSV issue connector adapter

[adoLime]

User Story

As an admin, I want to import a Jira issue export (CSV) and ingest the issues into the canonical artifact store, so that project tickets become searchable knowledge in the chat without a live Jira API integration.

Context & Motivation

• Type: Functional
• Parent epic: 03 EPIC - Connectors & Artifact Ingestion #52 (Connectors & Artifact Ingestion)
• Teams: team:backend (lead)
• Implementation repo: sprintstart-backend

Dependencies

• Depends on: [Story]: Canonical artifact schema and metadata normalization #161 (canonical artifact schema).
• Downstream: [Story]: Indexing pipeline — chunk, embed & store canonical artifacts (source-agnostic) #162 (indexing pipeline) chunks/embeds the artifacts this connector produces — required for the ingested Jira data to be searchable in chat.
• Relates to: [Story]: GitHub repository connector v0 (commits, files, issues, PR metadata) #159 (GitHub connector — shares mapper/provenance patterns), [Story]: Ingestion run history (PM view) #100 (ingestion run history).
• Note: Recommended as a Sprint 2 stretch goal — schedule after the GitHub connector is functional, since both compete for the same backend capacity.

Acceptance Criteria

• Given a Jira CSV export uploaded via the ingestion endpoint, when parsed, then each row becomes a canonical artifact with: summary -> title, description -> body, plus key, status, type, assignee, labels as metadata.
• Given a CSV with custom/unexpected columns, when parsed, then known fields map and unknown columns are preserved as raw metadata (no data loss, no crash).
• Given a re-import of the same export, when processed, then issues are matched by Jira key + hash and updated, not duplicated.
• Given a malformed row, when parsing, then that row is reported as failed and the rest import (partial success).
• Given each imported issue, when stored, then provenance is set: source_system=jira, source_id=<issue key>, ingestion_run_id.
• OpenAPI documented; a sample Jira export imports end-to-end on dev and is queryable via chat.

Sub-Tasks

• CSV upload/parse endpoint (reuse [Story]: Backend Multi-MD upload API + storage (with image handling) #131 multipart pattern)
• Column mapping config (Jira default columns -> canonical fields)
• Mapper: Jira row -> canonical artifact + chunks
• Key+hash dedupe / update logic
• Partial-success error reporting
• Provenance fields ([Story]: Ingestion run history (PM view) #100)
• OpenAPI annotation + smoke test with a sample export