feat: add Logs tab with cursor-paginated search, level filters, and live tail

- Extend GET /api/v1/logs with cursor pagination, multi-level filtering,
  optional application scoping, and level count aggregation
- Add exchangeId, instanceId, application, mdc fields to log responses
- Refactor ClickHouseLogStore with keyset pagination (N+1 pattern)
- Add LogSearchRequest/LogSearchResponse core domain records
- Create LogSearchPageResponse wrapper DTO
- Add Logs as 4th content tab (Exchanges | Dashboard | Runtime | Logs)
- Implement LogSearch component with debounced search, level filter bar,
  expandable log entries, cursor pagination, and live tail mode
- Add cross-navigation: exchange header → logs, log tab → logs tab
- Update ClickHouseLogStoreIT with cursor, multi-level, cross-app tests

Closes: #104

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cameleer3-server-core/src/main/java/com/cameleer3/server/core/search/LogSearchRequest.java

@@ -0,0 +1,44 @@
+package com.cameleer3.server.core.search;
+
+import java.time.Instant;
+import java.util.List;
+
+/**
+ * Immutable search criteria for querying application logs.
+ *
+ * @param q           free-text search across message and stack trace
+ * @param levels      log level filter (e.g. ["WARN","ERROR"])
+ * @param application application ID filter (nullable = all apps)
+ * @param instanceId  agent instance ID filter
+ * @param exchangeId  Camel exchange ID filter
+ * @param logger      logger name substring filter
+ * @param from        inclusive start of time range (required)
+ * @param to          inclusive end of time range (required)
+ * @param cursor      ISO timestamp cursor for keyset pagination
+ * @param limit       page size (1-500, default 100)
+ * @param sort        sort direction: "asc" or "desc" (default "desc")
+ */
+public record LogSearchRequest(
+        String q,
+        List<String> levels,
+        String application,
+        String instanceId,
+        String exchangeId,
+        String logger,
+        Instant from,
+        Instant to,
+        String cursor,
+        int limit,
+        String sort
+) {
+
+    private static final int DEFAULT_LIMIT = 100;
+    private static final int MAX_LIMIT = 500;
+
+    public LogSearchRequest {
+        if (limit <= 0) limit = DEFAULT_LIMIT;
+        if (limit > MAX_LIMIT) limit = MAX_LIMIT;
+        if (sort == null || !"asc".equalsIgnoreCase(sort)) sort = "desc";
+        if (levels == null) levels = List.of();
+    }
+}

cameleer3-server-core/src/main/java/com/cameleer3/server/core/search/LogSearchResponse.java

@@ -0,0 +1,21 @@
+package com.cameleer3.server.core.search;
+
+import com.cameleer3.server.core.storage.LogEntryResult;
+
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Log search result with cursor-based pagination and level aggregation.
+ *
+ * @param data        matching log entries for the current page
+ * @param nextCursor  ISO timestamp cursor for the next page (null if no more)
+ * @param hasMore     whether more results exist beyond this page
+ * @param levelCounts count of matching logs per level (unaffected by level filter)
+ */
+public record LogSearchResponse(
+        List<LogEntryResult> data,
+        String nextCursor,
+        boolean hasMore,
+        Map<String, Long> levelCounts
+) {}

cameleer3-server-core/src/main/java/com/cameleer3/server/core/storage/LogEntryResult.java

@@ -1,6 +1,8 @@
 package com.cameleer3.server.core.storage;
 
-import java.time.Instant;
+import java.util.Map;
 
 public record LogEntryResult(String timestamp, String level, String loggerName,
-                             String message, String threadName, String stackTrace) {}
+                             String message, String threadName, String stackTrace,
+                             String exchangeId, String instanceId, String application,
+                             Map<String, String> mdc) {}

cameleer3-server-core/src/main/java/com/cameleer3/server/core/storage/LogIndex.java

@@ -1,15 +1,14 @@
 package com.cameleer3.server.core.storage;
 
 import com.cameleer3.common.model.LogEntry;
+import com.cameleer3.server.core.search.LogSearchRequest;
+import com.cameleer3.server.core.search.LogSearchResponse;
 
-import java.time.Instant;
 import java.util.List;
 
 public interface LogIndex {
 
-    List<LogEntryResult> search(String applicationId, String instanceId, String level,
-                                String query, String exchangeId,
-                                Instant from, Instant to, int limit);
+    LogSearchResponse search(LogSearchRequest request);
 
     void indexBatch(String instanceId, String applicationId, List<LogEntry> entries);
 }