Add bookspy and unify spy modes

[luke560]

Adds /bookspy and unifies the spy on/off flags into a single shared mode enum so all four spies filter the same way.

/signspy is in this PR because release/v26.9-sirius forked from prod just before the PR merged, so signspy does not exist on this branch. The first four commits are that feature with two conflicts resolved for sirius: PlayerData.saveTo() dropped since sirius removes ConfigSavable from PlayerData and persistence now lives in GenericPlayerRepository; ranks.yml dropped in favor of ranks.json.

The last commit is the new work:

SpyMode

player/CommandSpyMode.java is replaced by player/SpyMode.java (OFF, OPS, ADMINS, ALL) with a single shows(boolean senderIsAdmin) used by CommandSpy, PotionSpy, SignSpy, and BookSpy.

All four commands take the same argument and tab complete the same values [ops | admins | all | off]. A bare /signspy or /bookspy enables OPS, so admin edits stay out of the way by default. A bare /cmdspy or /potionspy still enables ALL, unchanged behavior.

Unknown modes are now rejected instead of disabling the spy. The lenient parser is deliberately named fromStorage rather than fromString: EnumArgumentResolver prefers a static fromString over its own lookup, so naming it that would make e.g. /signspy opss resolve to OFF.

/bookspy

BookSpy listens to PlayerEditBookEvent and reports edits in the same shape as SignSpy, with a per page line-level diff:

shroomp edited book (page 14) +'the new line', -'the line that went away'
shroomp edited book (pages 2, 4, 7) +'first'[...] (and 3 more)
shroomp signed book 'Abolish OP Rights' [Read Book]

Buttons are [See Edit | Read Book], or just [Read Book] for a book's first write, where both would open the same page. See Edit opens at the first edited page; Read Book opens the whole book from page 1. Paper's openBook can't be told which page to open at, so See Edit hands over a copy sliced to start at that page.

Closing a book without changing it is ignored, as is a new blank draft. Signing is reported separately. Output is capped with [...] and (and N more) markers so a large book can't flood chat.

Storage

The players table gains potion_spy_mode, sign_spy_mode, and book_spy_mode (TEXT/VARCHAR(16), default 'off') across the SQLite, MySQL, and PostgreSQL adapters, with addColumnIfMissing migrations for existing databases. The boolean potion_spy column is gone.

Legacy yaml still imports correctly: PlayerData.loadFrom maps the old potion_spy and sign_spy booleans to all, and that is the path YamlMigrationService.migratePlayers uses.

The spy mode getters null-coalesce to OFF because PlayerList snapshots PlayerData through Gson, which allocates the object without running field initializers, so a snapshot written before a mode existed comes back with the field unset.