fix(i18n): replace "(s)" parenthetical plurals flagged by Weblate

[lstein]

Summary

• Hosted Weblate flagged 11 strings in en.json for the plural-form check because they used the word(s) parenthetical idiom — a construct that can't be translated cleanly into languages with multiple plural categories (Russian, Arabic, Polish, etc.).
• 5 static UI strings (Upload Image(s), Enter hotkey(s)…, model file(s), Incompatible LoRA(s) added, raster layer(s)) rephrased to plain plural form.
• 6 count-driven strings (bulk delete / reidentify confirmations and toasts) split into proper i18next _one / _other key pairs. Every call site already passes count: …, so no .ts / .tsx changes were needed — i18next picks the correct form automatically.

Notes

• The _one form of reidentifyModelsConfirm was also corrected from …re-probe their weights files… to …re-probe its weights file… so the singular grammar reads naturally.
• Other locales (de.json, etc.) are unaffected at runtime — i18next falls back to en.json for missing keys, and translators will pick up the new key shape on the next Weblate sync.

Test plan

• Verify Bulk Delete confirmation reads correctly for 1 model vs. N models.
• Verify Bulk Reidentify confirmation reads correctly for 1 model vs. N models (note grammar shift on weights file/files).
• Verify the post-action toasts (modelsDeleted, someModelsFailedToDelete, modelsReidentified, someModelsFailedToReidentify) render the right singular/plural form.
• Confirm the hotkey input placeholder, multi-upload button tooltip, inplace-install description, incompatible-LoRA warning, and denoising-strength tooltip all render without (s).
• Confirm Weblate's plural-form warnings on en.json clear after the next sync.

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