fix: sync user annotation file with database on Reset Annotations

[Copilot]

After "Update Database" replaces variants in the database, "Reset Annotations" would leave the user's annotation file incongruent — stale rows (removed from DB) persisted in the file, and new DB rows were never added.

Changes

R/admin_utils.R — reset_user_annotations()

Before clearing annotation columns, sync the user file's rows against the current database state:

• Remove stale rows: any row whose coordinates|REF|ALT composite key no longer exists in the DB is dropped from the user file
• Append new rows: any DB entry not yet in the user file is appended with all annotation columns blank
• Vote-count decrement logic now operates only on the filtered (still-in-DB) rows
• Re-randomise row order: after all sync operations, the full row order is shuffled using a fresh digest-based seed (same algorithm as the initial login flow), so the user gets a new voting sequence that places new rows at random positions
• Update images_randomisation_seed: the new seed is written to images_randomisation_seed in the user's _info.json alongside the existing vote_input_methods reset

# Sync before clearing annotation columns
db_entries <- DBI::dbGetQuery(db_pool, "SELECT coordinates, REF, ALT FROM annotations")

user_keys <- paste(annotations_df$coordinates, annotations_df$REF, annotations_df$ALT, sep = "|")
db_keys   <- paste(db_entries$coordinates,      db_entries$REF,      db_entries$ALT,      sep = "|")

# Drop rows no longer in DB
annotations_df <- annotations_df[user_keys %in% db_keys, , drop = FALSE]
user_keys      <- user_keys[user_keys %in% db_keys]

# Track new DB rows to append after reset
new_db_mask <- !db_keys %in% user_keys

# ... after building reset_df and appending new rows ...

# Re-randomise
randomisation_seed <- strtoi(substr(digest::digest(paste0(annotation_file_path, Sys.time()), algo = "crc32"), 1, 7), base = 16)
set.seed(randomisation_seed)
reset_df <- reset_df[sample(seq_len(nrow(reset_df))), , drop = FALSE]

tests/testthat/test-admin-reset-annotations.R

Three new test cases:

• Rows removed from DB → dropped from user file; vote counts decremented only for retained rows
• Rows added to DB → appended to user file with blank annotations
• Already-congruent file + DB → unchanged row count (existing behaviour preserved)

Updated existing test: images_randomisation_seed is now verified to be updated to a new numeric value on every reset (not preserved).

[IvoLeist]

After appending the new rows the row order should be randomised again
Do not forget to update the images_randomisation_seed in _info.json