feat(presets): upgrade default models to Opus 5, GPT-5.6 Sol and Gemini 3.6 Flash

Bump the default model IDs across every preset file and the downstream
defaults that mirror them:

- claude-opus-4-8 / anthropic/claude-opus-4.8 / global.anthropic.claude-opus-4-8
  -> claude-opus-5, covering all three naming forms
- gpt-5.5 and the bare gpt-5.6 -> gpt-5.6-sol
- gemini-3.5-flash -> gemini-3.6-flash

Add gemini-3.6-flash to the built-in pricing seed (1.50 in / 7.50 out /
0.15 cache read per million). The seed runs INSERT OR IGNORE on every
startup, so existing databases pick the row up without overriding prices
the user edited by hand.

Advance the Claude Desktop opus route ID in step with the frontend SSOT:
CURRENT_OPUS_ROUTE_ID becomes claude-opus-5 and claude-opus-4-8 takes over
the LEGACY slot, so route IDs stored in existing user configs still resolve
through is_compatible_opus_route_alias.

Also sync omo.ts recommendations, form placeholders, the SudoCode partner
blurb and all four locales, plus the preset assertions that pin these IDs.

src-tauri/src/database/schema.rs

@@ -1855,6 +1855,15 @@ impl Database {
             ("gpt-4.1", "GPT-4.1", "2", "8", "0.50", "0"),
             ("gpt-4.1-mini", "GPT-4.1 Mini", "0.40", "1.60", "0.10", "0"),
             ("gpt-4.1-nano", "GPT-4.1 Nano", "0.10", "0.40", "0.025", "0"),
+            // Gemini 3.6 系列
+            (
+                "gemini-3.6-flash",
+                "Gemini 3.6 Flash",
+                "1.50",
+                "7.50",
+                "0.15",
+                "0",
+            ),
             // Gemini 3.5 系列
             (
                 "gemini-3.5-flash",