Add exclude patterns, snapshot prune, and other improvements

- Implement exclude patterns with anchored pattern support:
  - Patterns starting with / only match from root of source dir
  - Unanchored patterns match anywhere in path
  - Support for glob patterns (*.log, .*, **/*.pack)
  - Directory patterns skip entire subtrees
  - Add gobwas/glob dependency for pattern matching
  - Add 16 comprehensive tests for exclude functionality

- Add snapshot prune command to clean orphaned data:
  - Removes incomplete snapshots from database
  - Cleans orphaned files, chunks, and blobs
  - Runs automatically at backup start for consistency

- Add snapshot remove command for deleting snapshots

- Add VAULTIK_AGE_SECRET_KEY environment variable support

- Fix duplicate fx module provider in restore command

- Change snapshot ID format to hostname_YYYY-MM-DDTHH:MM:SSZ

internal/database/schema.sql

@@ -28,6 +28,9 @@ CREATE TABLE IF NOT EXISTS file_chunks (
     FOREIGN KEY (chunk_hash) REFERENCES chunks(chunk_hash)
 );
 
+-- Index for efficient chunk lookups (used in orphan detection)
+CREATE INDEX IF NOT EXISTS idx_file_chunks_chunk_hash ON file_chunks(chunk_hash);
+
 -- Chunks table: stores unique content-defined chunks
 CREATE TABLE IF NOT EXISTS chunks (
     chunk_hash TEXT PRIMARY KEY,
@@ -56,6 +59,9 @@ CREATE TABLE IF NOT EXISTS blob_chunks (
     FOREIGN KEY (chunk_hash) REFERENCES chunks(chunk_hash)
 );
 
+-- Index for efficient chunk lookups (used in orphan detection)
+CREATE INDEX IF NOT EXISTS idx_blob_chunks_chunk_hash ON blob_chunks(chunk_hash);
+
 -- Chunk files table: reverse mapping of chunks to files
 CREATE TABLE IF NOT EXISTS chunk_files (
     chunk_hash TEXT NOT NULL,
@@ -67,6 +73,9 @@ CREATE TABLE IF NOT EXISTS chunk_files (
     FOREIGN KEY (file_id) REFERENCES files(id) ON DELETE CASCADE
 );
 
+-- Index for efficient file lookups (used in orphan detection)
+CREATE INDEX IF NOT EXISTS idx_chunk_files_file_id ON chunk_files(file_id);
+
 -- Snapshots table: tracks backup snapshots
 CREATE TABLE IF NOT EXISTS snapshots (
     id TEXT PRIMARY KEY,
@@ -96,6 +105,9 @@ CREATE TABLE IF NOT EXISTS snapshot_files (
     FOREIGN KEY (file_id) REFERENCES files(id)
 );
 
+-- Index for efficient file lookups (used in orphan detection)
+CREATE INDEX IF NOT EXISTS idx_snapshot_files_file_id ON snapshot_files(file_id);
+
 -- Snapshot blobs table: maps snapshots to blobs
 CREATE TABLE IF NOT EXISTS snapshot_blobs (
     snapshot_id TEXT NOT NULL,
@@ -106,6 +118,9 @@ CREATE TABLE IF NOT EXISTS snapshot_blobs (
     FOREIGN KEY (blob_id) REFERENCES blobs(id)
 );
 
+-- Index for efficient blob lookups (used in orphan detection)
+CREATE INDEX IF NOT EXISTS idx_snapshot_blobs_blob_id ON snapshot_blobs(blob_id);
+
 -- Uploads table: tracks blob upload metrics
 CREATE TABLE IF NOT EXISTS uploads (
     blob_hash TEXT PRIMARY KEY,
@@ -115,4 +130,7 @@ CREATE TABLE IF NOT EXISTS uploads (
     duration_ms INTEGER NOT NULL,
     FOREIGN KEY (blob_hash) REFERENCES blobs(blob_hash),
     FOREIGN KEY (snapshot_id) REFERENCES snapshots(id)
-);
+);
+
+-- Index for efficient snapshot lookups
+CREATE INDEX IF NOT EXISTS idx_uploads_snapshot_id ON uploads(snapshot_id);