feat: direct subscription fetching, URI parser, FLClashX compatibility

- Fetch subscriptions directly via httpx (mihomo UA → YAML, xray-checker → base64 URI list)
- Add uri_parser.py: vless/vmess/ss/trojan/hysteria2 URI → Mihomo proxy dicts
- Fix YAML quoting for Go parser (strings starting with special chars)
- Remove hidden:true and proxy-providers from delivered configs
- Inject all service groups into GLOBAL proxies for FLClashX group discovery
- Strip placeholder proxy-providers (e.g. "subscription") not in DB
- Fix Mihomo healthcheck: add Bearer auth header
- Add README

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

app/tests/test_routes.py

@@ -219,11 +219,12 @@ async def test_add_subscription(http_client, db_session):
     db_session.add(config)
     await db_session.commit()
 
-    resp = await http_client.post(
-        f"/configs/{config.id}/subscriptions/new",
-        data={"name": "mysub", "url": "https://example.com/sub"},
-        follow_redirects=False,
-    )
+    with patch("main.write_and_reload_mihomo", new_callable=AsyncMock):
+        resp = await http_client.post(
+            f"/configs/{config.id}/subscriptions/new",
+            data={"name": "mysub", "url": "https://example.com/sub"},
+            follow_redirects=False,
+        )
     assert resp.status_code == 303
 
     result = await db_session.execute(
@@ -246,7 +247,8 @@ async def test_delete_subscription(http_client, db_session):
     await db_session.commit()
     sub_id = sub.id
 
-    resp = await http_client.post(f"/subscriptions/{sub_id}/delete", follow_redirects=False)
+    with patch("main.write_and_reload_mihomo", new_callable=AsyncMock):
+        resp = await http_client.post(f"/subscriptions/{sub_id}/delete", follow_redirects=False)
     assert resp.status_code == 303
 
     result = await db_session.execute(select(Subscription).where(Subscription.id == sub_id))