feat: Phase 3 - Habits + Projects CRUD API, frontend, completions, sections

Habits REST API:
- GET/POST /api/domains/[domainId]/habits (list with filters, create)
- GET/PATCH/DELETE /api/domains/[domainId]/habits/[id] (detail, update, soft delete)
- POST /api/domains/[domainId]/habits/[id]/complete (completion + streak calc)
- GET /api/domains/[domainId]/habits/[id]/completions (list with date range)
- POST/DELETE /api/domains/[domainId]/habits/[id]/tags

Projects REST API:
- GET/POST /api/domains/[domainId]/projects (list with task counts, create)
- GET/PATCH/DELETE /api/domains/[domainId]/projects/[id] (detail with sections/tasks, update, soft delete)

Sections REST API:
- GET/POST /api/domains/[domainId]/projects/[projectId]/sections (list, create)
- GET/PATCH/DELETE /api/domains/[domainId]/projects/[projectId]/sections/[id]

Frontend:
- Habits page: checklist view, difficulty badges, streak display, filter
- Habit create dialog: name, description, frequency, difficulty, goal, unit, reminder, mood toggle
- Habit completion dialog: value, mood (1-5 emoji), notes
- Calendar heatmap: 365-day grid, color by value, hover tooltip
- Projects page: grid of cards with progress bars, status badges, tags
- Project detail page: sections board, drag tasks between sections
- Project create dialog: name, description, status, color picker, target date
- Section dialog: name, kind (section/milestone), status, target date

Keyboard shortcuts: c h (new habit), c p (new project), c s (new section)

All write routes follow AGENTS.md contract (Drizzle + recordActivity + pg_notify).
Build, typecheck, and 15 new tests pass.

apps/web/app/api/domains/[domainId]/habits/[id]/completions/route.ts

@@ -0,0 +1,60 @@
+// AGENT INSTRUCTION: After every write (INSERT/UPDATE/DELETE), you MUST:
+// 1. Insert activity feed entry
+// 2. Call pg.notify('project_e_events', JSON.stringify({ type, action, id, workspace_id }))
+// See AGENTS.md for full rules.
+
+import { NextRequest, NextResponse } from 'next/server';
+import { withAuth, requireWorkspaceAccess, createErrorResponse } from '@/lib/auth';
+import { db, habits, habitCompletions } from '@project-e/db';
+import { and, asc, desc, eq, gte, isNull, lte } from 'drizzle-orm';
+
+type RouteContext = { params: Promise<{ domainId: string; id: string }> };
+
+// GET /api/domains/[domainId]/habits/[id]/completions — List completions with date range
+export const GET = withAuth<RouteContext>(async (request: NextRequest, user, context) => {
+  const { domainId, id } = await context!.params;
+  await requireWorkspaceAccess(domainId);
+
+  // Verify habit exists
+  const [habit] = await db.select({ id: habits.id })
+    .from(habits)
+    .where(and(eq(habits.id, id), eq(habits.domainId, domainId), isNull(habits.deletedAt)))
+    .limit(1);
+
+  if (!habit) {
+    return createErrorResponse('NOT_FOUND', 'Habit not found', 404);
+  }
+
+  const { searchParams } = new URL(request.url);
+  const from = searchParams.get('from');
+  const to = searchParams.get('to');
+  const limit = Math.min(parseInt(searchParams.get('limit') || '365'), 1000);
+  const offset = parseInt(searchParams.get('offset') || '0');
+  const order = searchParams.get('order') || 'desc';
+
+  const conditions: any[] = [eq(habitCompletions.habitId, id)];
+
+  if (from) conditions.push(gte(habitCompletions.date, new Date(from)));
+  if (to) conditions.push(lte(habitCompletions.date, new Date(to)));
+
+  const orderFn = order === 'asc' ? asc : desc;
+
+  const [items, countResult] = await Promise.all([
+    db.select()
+      .from(habitCompletions)
+      .where(and(...conditions))
+      .orderBy(orderFn(habitCompletions.date))
+      .limit(limit)
+      .offset(offset),
+    db.select({ count: db.$count(habitCompletions) })
+      .from(habitCompletions)
+      .where(and(...conditions)),
+  ]);
+
+  return NextResponse.json({
+    items,
+    totalItems: Number(countResult[0]?.count || 0),
+    limit,
+    offset,
+  });
+});