Migrate backend from Python to Java Spring Boot

- Full Java 21 + Spring Boot 3.3 backend with Virtual Threads
- HikariCP connection pool for Oracle ADB
- JWT auth, Redis caching, OCI GenAI integration
- YouTube transcript extraction via API + Playwright browser fallback
- SSE streaming for bulk operations
- Scheduled daemon for channel scanning/video processing
- Mobile UI: collapse restaurant list to single row on selection
- Switch PM2 ecosystem config to Java backend

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend-java/src/main/java/com/tasteby/controller/ChannelController.java

@@ -0,0 +1,69 @@
+package com.tasteby.controller;
+
+import com.tasteby.repository.ChannelRepository;
+import com.tasteby.security.AuthUtil;
+import com.tasteby.service.CacheService;
+import org.springframework.http.HttpStatus;
+import org.springframework.web.bind.annotation.*;
+import org.springframework.web.server.ResponseStatusException;
+
+import java.util.List;
+import java.util.Map;
+
+@RestController
+@RequestMapping("/api/channels")
+public class ChannelController {
+
+    private final ChannelRepository repo;
+    private final CacheService cache;
+
+    public ChannelController(ChannelRepository repo, CacheService cache) {
+        this.repo = repo;
+        this.cache = cache;
+    }
+
+    @GetMapping
+    public List<Map<String, Object>> list() {
+        String key = cache.makeKey("channels");
+        String cached = cache.getRaw(key);
+        if (cached != null) {
+            try {
+                var mapper = new com.fasterxml.jackson.databind.ObjectMapper();
+                return mapper.readValue(cached,
+                        new com.fasterxml.jackson.core.type.TypeReference<>() {});
+            } catch (Exception ignored) {}
+        }
+        var result = repo.findAllActive();
+        cache.set(key, result);
+        return result;
+    }
+
+    @PostMapping
+    @ResponseStatus(HttpStatus.CREATED)
+    public Map<String, Object> create(@RequestBody Map<String, String> body) {
+        AuthUtil.requireAdmin();
+        String channelId = body.get("channel_id");
+        String channelName = body.get("channel_name");
+        String titleFilter = body.get("title_filter");
+        try {
+            String id = repo.create(channelId, channelName, titleFilter);
+            cache.flush();
+            return Map.of("id", id, "channel_id", channelId);
+        } catch (Exception e) {
+            if (e.getMessage() != null && e.getMessage().toUpperCase().contains("UQ_CHANNELS_CID")) {
+                throw new ResponseStatusException(HttpStatus.CONFLICT, "Channel already exists");
+            }
+            throw e;
+        }
+    }
+
+    @DeleteMapping("/{channelId}")
+    public Map<String, Object> delete(@PathVariable String channelId) {
+        AuthUtil.requireAdmin();
+        if (!repo.deactivate(channelId)) {
+            throw new ResponseStatusException(HttpStatus.NOT_FOUND, "Channel not found");
+        }
+        cache.flush();
+        return Map.of("ok", true);
+    }
+}