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/types/thought.go

@@ -30,9 +30,10 @@ type ThoughtAttachment struct {
 }
 
 type StoredFile struct {
-	ID        uuid.UUID  `json:"id"`
-	ThoughtID *uuid.UUID `json:"thought_id,omitempty"`
-	ProjectID *uuid.UUID `json:"project_id,omitempty"`
+	ID        int64      `json:"id"`
+	GUID      uuid.UUID  `json:"guid"`
+	ThoughtID *int64     `json:"thought_id,omitempty"`
+	ProjectID *int64     `json:"project_id,omitempty"`
 	Name      string     `json:"name"`
 	MediaType string     `json:"media_type"`
 	Kind      string     `json:"kind"`
@@ -46,25 +47,26 @@ type StoredFile struct {
 
 type StoredFileFilter struct {
 	Limit     int
-	ThoughtID *uuid.UUID
-	ProjectID *uuid.UUID
+	ThoughtID *int64
+	ProjectID *int64
 	Kind      string
 }
 
 type Thought struct {
-	ID              uuid.UUID       `json:"id"`
+	ID              int64           `json:"id"`
+	GUID            uuid.UUID       `json:"guid"`
 	Content         string          `json:"content"`
 	Embedding       []float32       `json:"embedding,omitempty"`
 	EmbeddingStatus string          `json:"embedding_status,omitempty"`
 	Metadata        ThoughtMetadata `json:"metadata"`
-	ProjectID       *uuid.UUID      `json:"project_id,omitempty"`
+	ProjectID       *int64          `json:"project_id,omitempty"`
 	ArchivedAt      *time.Time      `json:"archived_at,omitempty"`
 	CreatedAt       time.Time       `json:"created_at"`
 	UpdatedAt       time.Time       `json:"updated_at"`
 }
 
 type SearchResult struct {
-	ID         uuid.UUID       `json:"id"`
+	ID         int64           `json:"id"`
 	Content    string          `json:"content"`
 	Metadata   ThoughtMetadata `json:"metadata"`
 	Similarity float64         `json:"similarity"`
@@ -77,7 +79,7 @@ type ListFilter struct {
 	Topic           string
 	Person          string
 	Days            int
-	ProjectID       *uuid.UUID
+	ProjectID       *int64
 	IncludeArchived bool
 }