Tasks: GitHub Projects-style board filter / search / sort

[ReBoticsAI]

Summary

Add a GitHub Projects-style filter bar on Tasks boards so operators can narrow and order cards without leaving the kanban.

Follow-up from closed epic #259 (kanban parity). Swimlanes / group-by remain #274 (do not duplicate that work here).

Scope

• Filter bar on /tasks (linked and local boards)
• Search by title / body text
• Filter by common fields already on cards (priority, labels, assignees, milestone, column/Status) where data exists
• Sort options that match Projects board habits (e.g. priority, due/target date, updated)
• Clear filters / empty-state when nothing matches

Out of scope

• Swimlanes / group-by rows (Tasks: optional swimlanes / group-by on kanban (follow-up from #259) #274)
• Full Projects table or roadmap layouts
• New Project custom-field sync (separate field-parity issue)

Acceptance

• Board has a filter/search/sort control that persists for the session (or board preference if cheap)
• Filtering does not break drag-and-drop or GitHub push-on-edit for visible cards
• Works for local-only boards and GitHub-linked boards
• Short note in docs/features/tasks.md

Refs

• Closed: Epic: Tasks kanban parity with GitHub Projects board (+ GodMode extras) #259
• Related: Tasks: optional swimlanes / group-by on kanban (follow-up from #259) #274

[ReBoticsAI]

Shipped in #280 (merge 2d9604e).

Hostinger redeploy: ghcr.io/reboticsai/godmode@sha256:940e51ec7afd18f28cb516e0db75d78681308d6eaff2c93b20a3a29d6a9dfcd9. Health /api/health HTTP 200. Poll 60s and GitHub App env preserved.

[ReBoticsAI]

Shipped in #280. Hostinger redeployed to ghcr.io/reboticsai/godmode@sha256:940e51ec7afd18f28cb516e0db75d78681308d6eaff2c93b20a3a29d6a9dfcd9; /api/health returned 200.