chore(ios): P2 polish - strip headers, cleanup orphan UserDefaults, accessibility labels

[datlechin]

Summary

P2 polish pass bundling three independent items into one PR. Each item is small enough on its own that splitting into three PRs adds review overhead without payoff.

P2 #10 - Strip Xcode-generated file headers

Drop the 4-line //\n// X.swift\n// TableProMobile\n//\n boilerplate from every iOS source file. CLAUDE.md rule: no comments. Six files (drivers + SSH) had an extra one-liner description after the header; those descriptions are stripped too since the type names are self-explanatory and any non-obvious purpose belongs in a /// doc comment on the type, not as a floating top-of-file note.

Touched 58 files in TableProMobile/ and 9 in TableProWidget/.

P2 #9 - Cleanup orphan UserDefaults on connection delete

AppState.removeConnection now also calls clearPerConnectionPreferences(for:) which removes:

• lastTab.<uuid> (selected tab on Connected screen)
• lastDB.<uuid> (active database)
• lastSchema.<uuid> (active schema)
• lastQuery.<uuid> (last typed query in the editor)

Previously, deleting a connection silently leaked these four UserDefaults keys forever. Repeated add and delete cycles built up unbounded keychain-adjacent state.

P2 #8 - Accessibility labels on high-impact surfaces

Audit found 9 accessibility annotations across the entire app and zero hints. This pass adds the most-used surfaces:

• TableRow (table list): combines type, name, and row count into a single accessibility element with hint "Opens table data"
• ConnectionRow (connection list): combines type, display name, host or SQLite filename, and tag name into a single element with hint "Opens this connection"
• ConnectionList toolbar: Add Connection, Sync with iCloud, and Settings icon-only buttons gain explicit accessibilityLabel

Other toolbar items (Sort, Filter, Insert Row in DataBrowser; Edit Connection in ConnectedView) already had labels.

Test plan

• Header strip: app builds, no broken import statements (the strip is mechanical, but verify the diff in a couple of driver files)
• Add a connection, delete it, then defaults read the app's bundle ID: the four last*.<uuid> keys for that connection are gone
• VoiceOver on: navigate the connection list, hear "MySQL, Local, 127.0.0.1 port 3306. Opens this connection." Same shape for tables.
• VoiceOver on toolbar: hear "Add Connection. Button.", "Sync with iCloud. Button.", "Settings. Button."