refactor(catalog): the HTTP layer reads through queries and writes through the service

Channels, search and sync do no database work in their routes any more: reads go through
catalog/queries, writes through catalog/service, and a live search's ingest is catalog/search.
What a catalog route needs from Reader (a playlist's channels, a user's tag links, the feed
projection of results) it asks reader/queries and reader/service. The scheduler and the runs page
read channel titles and the work queue through catalog/queries. Catalog is fenced below its HTTP
layer: its owner filters go through userscope, it reads no other unit's tables, and its ingest
jobs commit only where they are named.

backend/.basedpyright/baseline.json

@@ -640,48 +640,6 @@
                 }
             }
         ],
-        "./app/routes/channels.py": [
-            {
-                "code": "reportReturnType",
-                "range": {
-                    "startColumn": 11,
-                    "endColumn": 11,
-                    "lineCount": 6
-                }
-            },
-            {
-                "code": "reportArgumentType",
-                "range": {
-                    "startColumn": 8,
-                    "endColumn": 15,
-                    "lineCount": 1
-                }
-            },
-            {
-                "code": "reportArgumentType",
-                "range": {
-                    "startColumn": 49,
-                    "endColumn": 56,
-                    "lineCount": 1
-                }
-            },
-            {
-                "code": "reportAttributeAccessIssue",
-                "range": {
-                    "startColumn": 38,
-                    "endColumn": 44,
-                    "lineCount": 1
-                }
-            },
-            {
-                "code": "reportAttributeAccessIssue",
-                "range": {
-                    "startColumn": 33,
-                    "endColumn": 39,
-                    "lineCount": 1
-                }
-            }
-        ],
         "./app/routes/discover.py": [
             {
                 "code": "reportInvalidTypeForm",
@@ -967,14 +925,6 @@
             }
         ],
         "./app/routes/scheduler.py": [
-            {
-                "code": "reportArgumentType",
-                "range": {
-                    "startColumn": 42,
-                    "endColumn": 55,
-                    "lineCount": 1
-                }
-            },
             {
                 "code": "reportOptionalMemberAccess",
                 "range": {
@@ -992,42 +942,6 @@
                 }
             }
         ],
-        "./app/routes/search.py": [
-            {
-                "code": "reportArgumentType",
-                "range": {
-                    "startColumn": 25,
-                    "endColumn": 31,
-                    "lineCount": 1
-                }
-            },
-            {
-                "code": "reportAttributeAccessIssue",
-                "range": {
-                    "startColumn": 6,
-                    "endColumn": 14,
-                    "lineCount": 1
-                }
-            }
-        ],
-        "./app/routes/sync.py": [
-            {
-                "code": "reportArgumentType",
-                "range": {
-                    "startColumn": 42,
-                    "endColumn": 65,
-                    "lineCount": 1
-                }
-            },
-            {
-                "code": "reportAttributeAccessIssue",
-                "range": {
-                    "startColumn": 42,
-                    "endColumn": 50,
-                    "lineCount": 1
-                }
-            }
-        ],
         "./app/sync/explore.py": [
             {
                 "code": "reportAttributeAccessIssue",