feat(backend): add knowledge base, innovation library and trends modules

Add knowledge item and innovation CRUD with search/filtering, published-only visibility for non-staff, admin publish/update, challenge dictionary, problem aggregation with trends (admin only) and canonical embedding text preparation for matchmaking.

backend/Controllers/KnowledgeItemsController.cs

@@ -0,0 +1,81 @@
+using Asp.Versioning;
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+using TarninaHub.Application.Abstractions;
+using TarninaHub.Application.Dtos;
+using TarninaHub.Application.Security;
+
+namespace TarninaHub.Controllers;
+
+[ApiController]
+[ApiVersion("1.0")]
+[Route("api/knowledge-items")]
+[Authorize]
+public class KnowledgeItemsController : ControllerBase
+{
+    private readonly IKnowledgeItemService _knowledgeItems;
+
+    public KnowledgeItemsController(IKnowledgeItemService knowledgeItems)
+    {
+        _knowledgeItems = knowledgeItems;
+    }
+
+    [HttpGet]
+    public async Task<ActionResult<IReadOnlyList<KnowledgeItemResponse>>> List(
+        [FromQuery] string? kind,
+        [FromQuery] string? challengeId,
+        [FromQuery] string? q,
+        CancellationToken cancellationToken)
+    {
+        var items = await _knowledgeItems.ListAsync(kind, challengeId, q, !IsStaff(), cancellationToken);
+
+        return Ok(items);
+    }
+
+    [HttpGet("{knowledgeItemId}")]
+    public async Task<ActionResult<KnowledgeItemResponse>> GetById(
+        string knowledgeItemId,
+        CancellationToken cancellationToken)
+    {
+        var item = await _knowledgeItems.GetAsync(knowledgeItemId, cancellationToken);
+
+        return item is null ? NotFound() : Ok(item);
+    }
+
+    [HttpPost]
+    [Authorize(Policy = Policies.OperatorOrAdmin)]
+    public async Task<ActionResult<KnowledgeItemResponse>> Create(
+        KnowledgeItemRequest request,
+        CancellationToken cancellationToken)
+    {
+        var created = await _knowledgeItems.CreateAsync(request, cancellationToken);
+
+        return CreatedAtAction(nameof(GetById), new { knowledgeItemId = created.Id }, created);
+    }
+
+    [HttpPut("{knowledgeItemId}")]
+    [Authorize(Policy = Policies.OperatorOrAdmin)]
+    public async Task<ActionResult<KnowledgeItemResponse>> Update(
+        string knowledgeItemId,
+        KnowledgeItemRequest request,
+        CancellationToken cancellationToken)
+    {
+        var updated = await _knowledgeItems.UpdateAsync(knowledgeItemId, request, cancellationToken);
+
+        return updated is null ? NotFound() : Ok(updated);
+    }
+
+    [HttpPost("{knowledgeItemId}/publish")]
+    [Authorize(Policy = Policies.OperatorOrAdmin)]
+    public async Task<ActionResult<KnowledgeItemResponse>> Publish(
+        string knowledgeItemId,
+        CancellationToken cancellationToken)
+    {
+        var published = await _knowledgeItems.PublishAsync(knowledgeItemId, cancellationToken);
+
+        return published is null ? NotFound() : Ok(published);
+    }
+
+    private bool IsStaff() =>
+        User.IsInRole(RoleNames.Operator) || User.IsInRole(RoleNames.Manager) || User.IsInRole(RoleNames.Admin);
+}