jira: auto-detect boards & epics when configuring an app's JIRA integration

[atomantic]

What

Configuring an app's JIRA integration used to require hand-typing a Board ID (a free-text field) — exactly how a board id silently goes stale (e.g. after a Server→Cloud migration, where board ids are reassigned). The app-config JIRA tab now auto-detects the workspace from the chosen instance + project:

• Board is a detected dropdown (id — name (type)) instead of free text. If the app's saved board id isn't among the project's live boards, it's flagged with an amber "pick a current one" warning (the stale value stays selectable so it isn't silently dropped). Falls back to manual entry if detection fails.
• The selected board shows its current active sprint as confirmation.
• Epic Key gained live search-by-name (type a name → pick from matching epics) and validation of a typed/pasted key — ✓ resolves as Epic / ⚠ wrong type / ⚠ no longer resolves.

How

• Backend (server/services/jira.js + routes/jira.js), mirroring the existing getProjects/searchEpics pattern:
  • GET /jira/instances/:id/projects/:key/boards → getBoards() (paginated Agile board list)
  • GET /jira/instances/:id/issues/:key → getIssue() (resolve a key for epic validation)
• Client: apiSystem.js wrappers (getJiraBoards, getJiraBoardSprints, searchJiraEpics, getJiraIssue) + EditAppDrawer.jsx UI. Board-reset on instance/project change is centralized in changeInstance/selectProject handlers so no call site forgets it (deliberately interaction-driven, not a projectKey effect that would wipe the saved board on mount before staleness detection runs). Epic field discriminates validate-vs-search via a key regex so only one request fires.

Review & tests

• /simplify pass (reuse/simplification/efficiency/altitude): applied the board-reset consolidation; skipped an EntityCombobox swap (its client-side filter + create-new + single-mode don't fit the epic field's server-search + dual key/name mode + validation footer).
• claude review pass: no high/medium defects; applied its one actionable finding (trim epicKey on save so it matches the validation).
• Tests: server jira.test.js 14/14, client EditAppDrawer.test.jsx 8/8; client lint clean.