Feature/implement pagination for epic picker

[pikann]

Summary

• Fixed a 400 error (page_size must be an integer between 1 and 200) that hit whenever the epic dropdown had more than a handful of epics, and separately whenever any task detail page was opened — the #-mention task picker (used in comments, task descriptions, and docs) was requesting page_size: 500 against a backend capped at 200.
• Replaced the epic picker's single oversized fetch with cursor-based infinite pagination (20/page) shared across board view, list view, and task detail — loading more now happens by scrolling to the bottom of the list instead of clicking a "Load more" button.
• Replaced the mention picker's "preload everything" pattern with a live, debounced server-side search (search param, matches title or #task_number), so it now correctly reaches every task in a project instead of silently missing anything past whatever page happened to be preloaded.
• Added a search box to every epic picker (task card, task row, task-detail properties panel), debounced and backed by its own cursor-paginated server search — typing narrows results, and scrolling loads further matches instead of filtering only the already-loaded page.
• Fixed a translation-key regression from the earlier pagination pass: board.taskCard/taskRow/taskContextMenu's "load more/loading epics" text referenced i18n keys that didn't exist in any locale. Consolidated all epic-picker strings into a shared epicPicker.* namespace across all 9 locales.

Test plan

• tsc -b clean
• biome check clean
• Reproduced the original page_size=500 400 error directly against the API, then confirmed the fixed calls succeed
• Verified debounced search (by title and #task_number) and cursor-based pagination via direct API calls against the local dev stack
• Manual click-through in a browser before merge (no browser session available in this environment to screenshot)

[pullfrog]

Important

One must-address finding — the #-mention task search fires a network request on every keystroke with no debounce. One nit inline and two in the body.

Reviewed changes — replaces the single useQuery fetch for all epic tasks with cursor-paginated useInfiniteQuery (20 items per page) across all epic picker UIs, adds a debounced server-side epic search box, and switches #-mention task lookup from preloaded client-side filtering to on-demand server-side search.

• Epic list pagination — interaction-layout.tsx and task-detail/index.tsx each create an useInfiniteQuery via epicTasksInfiniteQueryOptions, flatten pages, and build an EpicsPagination object threaded down through board-view, list-view, list-group, task-card, task-row, task-context-menu, and properties-panel.
• Epic search — new useEpicSearch hook wraps a debounced (300ms) useInfiniteQuery against searchEpicTasks; the picker swaps between search results and paginated epics based on isEpicSearching. Added to task-card, task-row, and properties-panel.
• Infinite scroll — createEpicScrollHandler in view-utils.ts auto-loads the next page when the picker scrolls within 48px of the bottom; applied to every epic list container including the right-click context menu.
• #-mention task search — useMentionData no longer preloads tasks; MentionSuggestionMenus calls searchMentionableTasks on demand for whatever the user types after #. Three BlockNote consumers (doc-editor, description-section, comment-blocknote) pass projectId instead of tasks.
• i18n — adds epicPicker namespace across 9 locales.

ℹ️ Nitpicks

• use-project-realtime.ts:25 — the comment still references epicTasksQueryOptions, which was renamed to epicTasksInfiniteQueryOptions. The invalidation logic is unaffected (the shared ["projects", projectId, "tasks"] prefix still covers it), but the comment is stale.
• interaction-layout.tsx and task-detail/index.tsx both repeat the same useInfiniteQuery → flatMap → EpicsPagination construction. Consider extracting a shared useEpicTasksPagination hook to keep the wiring in one place.

  ^{｜ Fix all ➔ ｜ Fix 👍s ➔ ｜ View workflow run ｜ Using DeepSeek Pro (free via Pullfrog for OSS) (Kimi K2 not used — the program covers this model; add its provider key to run your pick) ｜ 𝕏}

[pullfrog]

✅ No new issues found in this commit.

Reviewed changes — one lint commit since the prior review at 751e990.

• Lint fix — task-detail/index.tsx import reformatted from single-line to multi-line for useInfiniteQuery and friends. No behavioral change.

  ^{｜ Fix it ➔ ｜ View workflow run ｜ Using DeepSeek Pro (free via Pullfrog for OSS) (Kimi K2 not used — the program covers this model; add its provider key to run your pick) ｜ 𝕏}

[pullfrog]

ℹ️ No new issues in this commit. The open debounce thread from the prior review (mention-suggestion-menus.tsx:59) is unchanged by these additions and remains outstanding.

Reviewed changes — adds infinite-scroll pagination to the team member selection dialog, replacing a page_size=500 one-shot fetch that exceeds the backend's 200-item cap. Follows the same cursor‑pagination pattern already established by the epic picker.

• usersInfiniteQueryOptions — new infinite‑query export in admin-api.ts that pages through the user list 20 at a time, mirroring epicTasksInfiniteQueryOptions.
• AddMemberDialog pagination — switched from useQuery(getUsers(1, 500)) to useInfiniteQuery(usersInfiniteQueryOptions()) with handleUsersListScroll auto‑loading the next page on scroll‑near‑bottom.
• i18n — added team.addMemberDialog.loadingMore across all 9 locales.

  ^{｜ Fix it ➔ ｜ View workflow run ｜ Using DeepSeek Pro (free via Pullfrog for OSS) (Kimi K2 not used — the program covers this model; add its provider key to run your pick) ｜ 𝕏}

[pullfrog]

✅ No new issues found.

Reviewed changes — two commits since the prior review at 6c6eb04: a test-infrastructure fix and a debounce for the #-mention task search.

• useDebouncedAsyncCallback — new hook in hooks/use-debounced-callback.ts that extends the existing useDebouncedCallback for async callbacks needing a return value. Every call within the debounce window shares the single fetch fired once the timer settles, with all callers' promises resolved from the same result.
• Debounced mention search — mention-suggestion-menus.tsx now wraps searchMentionableTasks in useDebouncedAsyncCallback with a 300ms delay, so rapid typing after # fires at most one network request. Also skips client-side filterSuggestionItems for tasks since the server already filters by query.
• Test infrastructure — task-card.test.tsx wraps all render calls with a QueryClientProvider since TaskCard now unconditionally calls useEpicSearch (which uses useInfiniteQuery).
• i18n — adds epicPicker and team.addMemberDialog.loadingMore keys across all 9 locales.

  ^{｜ View workflow run ｜ Using DeepSeek Pro (free via Pullfrog for OSS) (Kimi K2 not used — the program covers this model; add its provider key to run your pick) ｜ 𝕏}