fix(search): gallery library per-word search with LIKE escaping (#6584)

Gallery search built a single `%{search}%` LIKE, so multi-word queries only matched the exact adjacent phrase ("red car" missed "a car that is red") and literal % / _ acted as SQL wildcards. Split on whitespace and require each token to match (prompt OR tags OR ai_tags), escaping LIKE wildcards per token; same escaping for the tag filter. Promote _escape_like to public escape_like_pattern() shared helper.

Part of #2123.

Tests: tests/test_gallery_search_multiword.py (5 tests); 4 fail pre-fix, 5 pass post-fix. Neighbors (session_search, gallery null-user, shims): 25 passed.

routes/gallery/gallery_routes.py

@@ -18,6 +18,7 @@ from fastapi import APIRouter, HTTPException, Query, Request
 from core.database import SessionLocal, GalleryImage, GalleryAlbum, ModelEndpoint
 from core.database import Session as DbSession
 from src.auth_helpers import get_current_user, owner_filter, require_privilege
+from src.session_search import escape_like_pattern
 from src.upload_limits import (
     read_upload_limited,
     GALLERY_UPLOAD_MAX_BYTES,
@@ -1184,15 +1185,18 @@ def setup_gallery_routes() -> APIRouter:
             )
             q = _owner_filter(q, user)
 
-            # Search filter (prompt + tags + ai_tags)
+            # Per-term AND search: a single `%foo bar%` LIKE only matched the
+            # exact phrase, so "red car" missed "a car that is red".
+            # LIKE wildcards are escaped per token.
             if search:
-                term = f"%{search}%"
                 from sqlalchemy import or_
-                q = q.filter(or_(
-                    GalleryImage.prompt.ilike(term),
-                    GalleryImage.tags.ilike(term),
-                    GalleryImage.ai_tags.ilike(term),
-                ))
+                for tok in search.split():
+                    term = f"%{escape_like_pattern(tok)}%"
+                    q = q.filter(or_(
+                        GalleryImage.prompt.ilike(term, escape="\\"),
+                        GalleryImage.tags.ilike(term, escape="\\"),
+                        GalleryImage.ai_tags.ilike(term, escape="\\"),
+                    ))
 
             # Tag filter. The UI stacks multiple tag pills by passing them
             # comma-separated — each tag adds a separate AND-filter so the
@@ -1203,9 +1207,10 @@ def setup_gallery_routes() -> APIRouter:
                 for one in (t.strip() for t in tag.split(",")):
                     if not one:
                         continue
+                    safe_tag = f"%{escape_like_pattern(one)}%"
                     q = q.filter(_or(
-                        GalleryImage.tags.ilike(f"%{one}%"),
-                        GalleryImage.ai_tags.ilike(f"%{one}%"),
+                        GalleryImage.tags.ilike(safe_tag, escape="\\"),
+                        GalleryImage.ai_tags.ilike(safe_tag, escape="\\"),
                     ))
 
             # Model filter