Relyt and AnalyticDB vector providers generate malformed SQL for metadata-filtered search

## Relyt and AnalyticDB vector providers generate malformed SQL for metadata-filtered search

Two related static defects in the vdb provider packages cause every metadata-filtered vector search on Relyt to fail with a SQL syntax error, and every metadata-filtered vector search on AnalyticDB to fail on PostgreSQL 15+.

### 1. Relyt: doubled-quoted metadata key

**File:** `api/providers/vdb/vdb-relyt/src/dify_vdb_relyt/relyt_vector.py`, lines 258 & 260

```python
conditions = [
f"metadata->>'{key!r}' in ({', '.join(map(repr, value))})"
if len(value) > 1
else f"metadata->>'{key!r}' = {value[0]!r}"
for key, value in filter.items()
]
```

`{key!r}` wraps the key in `'…'`, but the f-string already wraps it in `'…'` for the JSONB operator, so `key="document_id"` renders as:

```sql
metadata->>''document_id'' = ''
```

…which is a syntax error in PostgreSQL/Relyt. Every metadata-filtered search through Relyt breaks.

**Fix:** drop the `!r` so the key is interpolated as a plain identifier:

```python
f"metadata->>'{key}' = {value[0]!r}"
```

The value-side `repr()` is correct and stays; values are UUIDs or system-controlled strings, so `repr()` quoting is sufficient.

### 2. AnalyticDB: missing space between `WHERE 1=1` and `AND …`

**File:** `api/providers/vdb/vdb-analyticdb/src/dify_vdb_analyticdb/analyticdb_vector_sql.py`, line 215

```python
where_clause = "WHERE 1=1"
if document_ids_filter:
document_ids = ", ".join(f"'{id}'" for id in document_ids_filter)
where_clause += f"AND metadata_->>'document_id' IN ({document_ids})"
```

Concatenation yields:

```sql
WHERE 1=1AND metadata_->>'document_id' IN (...)
```

Older PostgreSQL versions tolerate this; PostgreSQL 15+ (and current AnalyticDB builds) reject `1AND` as a malformed numeric literal: "trailing junk after numeric literal". Every filtered vector search on a current AnalyticDB backend fails.

**Fix:** add a trailing space:

```python
where_clause = "WHERE 1=1 "
```

### Notes

- Both defects are verifiable by reading the file; I have not run live Relyt/AnalyticDB backends.
- No user-controlled quotes currently reach the SQL paths in either provider, so this issue is a functional defect (broken filtered search) rather than a security vulnerability. Other vdb providers (Hologres, OceanBase) use parameterized queries; Relyt and AnalyticDB stand out as the last two using string interpolation for filter construction.