refactor(store,tools): migrate IDs from UUID to bigserial int64

All internal entity lookups now use bigserial primary keys (int64) while
GUIDs are retained for external/public identification. Updated store
functions (TouchProject, UpdateThoughtMetadata, AddThoughtAttachment) to
query by id instead of guid, added GetThoughtByID, changed semanticSearch
and all tool helpers to use *int64 project IDs, and updated retry/backfill
workers to use int64 thought IDs throughout.

internal/generatedmodels/sql_public_thought_links.go

@@ -9,7 +9,7 @@ import (
 
 type ModelPublicThoughtLinks struct {
 	bun.BaseModel `bun:"table:public.thought_links,alias:thought_links"`
-	ID            resolvespec_common.SqlInt32     `bun:"id,type:serial,pk,autoincrement," json:"id"`
+	ID            resolvespec_common.SqlInt64     `bun:"id,type:bigserial,pk,autoincrement," json:"id"`
 	CreatedAt     resolvespec_common.SqlTimeStamp `bun:"created_at,type:timestamptz,default:now(),nullzero," json:"created_at"`
 	FromID        int64                           `bun:"from_id,type:bigint,notnull," json:"from_id"`
 	Relation      resolvespec_common.SqlString    `bun:"relation,type:text,notnull," json:"relation"`